


Peridot Tells The Story of Everything

by KilldeerCheer



Category: Steven Universe (Cartoon)
Genre: Adventure, But nearly everything depicted is with the highest historical/scientific accuracy, Educational, Humor, Picture 'Magic School Bus' meets 'Peabody & Sherman' meets 'Cartoon History of the Universe', Self Insert, Slight warnings for all the usual stuff found in historical depictions, Technically Historical Fiction? I guess?, Time Travel, Will include notes on references used, World History, human history
Language: English
Status: In-Progress
Published: 2020-01-06
Updated: 2020-01-18
Packaged: 2021-02-27 16:21:44
Rating: Teen And Up Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 8
Words: 39,731
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/22150096
Author URL: https://archiveofourown.org/users/KilldeerCheer/pseuds/KilldeerCheer
Summary: Nothing less than the history of the world, told from the perspective of everyone's favorite Era 2 Gem!AU: does not follow SU's canon history exactly.
Kudos: 7





	1. Prologue

_ Beach City Lighthouse Park - Summertime 2019 AD _

“Just a few more tweaks… errr this thing won’t go. Where. I. Need. It. To. Arrgahhhh!! Wait! Wait… almost… ah ha!” 

Letting out a cheerful huff, Peridot scoots herself from underneath what appears to be a vehicle of some sort. She had been tinkering with the gears and wires and felt that her work was complete. 

Wiping her brow, she turns to you, the reader.

“Hello! Ah, you’re right on time! Allow me to introduce myself, my name is Peridot Facet-2F5L Cut-5XG, but just Peridot will do. No need for formalities here: we’re going to be together for a while, so it’s best that we get comfortable and casual with each other.”

Peridot rests herself against the vehicle.

“It’s been a few years since I allied myself with the Crystal Gems and called the Earth my home, and I have to say I’ve grown quite attached to it. Thanks to Steven and his friends, my knowledge of this planet have risen, and with Connie’s suggesting that I try out the library, that understanding has only increased exponentially! That leaves me in a good position of authority on all Earth matters, if I do say so myself! Nehehehehe!”

“That’s why I built this!” Peridot exclaims, motioning her arms towards the strange vehicle. The base design looks like her old escape pod, with the walking limbs splayed underneath. The holoscreen was not deployed, giving you a good view of the opening, which was now full of multicolored string-lights and a small chest. 

“Feast your eyes on my… wait, drum roll please!” Peridot motions her hands likewise, “... my time machine! Yes, please, bask in its glory.” She gives a small curtsey. “Thank you, thank you.”

Peridot readjusts herself. “We are about to embark on a fantastic adventure! Traveling around the world at the speed of light, encountering places and peoples lost in time, and seeing your species’ greatest accomplishments in real time! I, Peridot, will be your guide as I tell you the whole story of life, the universe, and everything!”

At that moment, Lapis Lazuli flies down next to her friend, looking at her and her vehicle with feigned curiosity. “Peridot, what are you up to?”

“I’m about to lead this human on a complete history of the world, with the help of my time machine that I just finished building!” Peridot replied, grinning widely.

Lapis clicked her tongue, “Peridot, people don’t read fanfictions to learn, they want to see characters like us fulfilling their kinky desires.”

“What?”

“What?”

“Oh come on Lapis! This will be more than just a ‘learning experience’ (at this Peridot makes quotes with her fingers), there’s action, drama, romance, political infighting-”

You already begin to lose interest and start walking away. Seeing this, Peridot runs over and grabs your hand gently. “WAIT! Wait! Don’t go, please! I promise, you don’t know what you’re missing! History doesn’t have to be boring and educational, there’s real magic here! Just… just give it a chance, please?” 

You look into Peridot's whimpering, puppy-dog eyes, and decide to stay.

“Yay! You won’t regret it! I promise!” Peridot leads you inside the time machine, taking her place at the control panel.

“Last call to board! What do you say Lapis?” Peridot smiles at her friend.

“I’ll pass. From what Steven’s told me, history has wars and battles, and I don’t feel like experiencing more violence. I’m sure you understand.” Lapis explains, rubbing the back of her neck.

“Say no more! You’ll hold down the fort for me?”

“Sure. Can I watch past where we left off on  _ Camp Pining Hearts _ ?”

“NO!”

“Peridot, we’ve rewatched this show hundreds of times! You already know what happens!”

“Err… fine. But we’re starting right back there when I return.”

“Deal.”

Peridot activates the time machine: everything dims as the bead-like lights begin to twinkle as the holoscreen seals you both inside. “There are snacks and other supplies in that chest in case you need them, but we should be good for now!”

Peridot sets the timer for ‘13.8 billion years ago’. 

“First stop… the beginning of the cosmos! Hang on tight!” Peridot presses a bright pink button on the holoscreen, and the time machine begins to hover upwards, its limbs receding inside. Lapis gives a thumbs up to Peridot who returns the gesture. Within seconds, the machine vanishes from view in a brilliant flash of color. 

And so the adventure begins! 

…

**_To Be Continued!_ **


	2. Once Upon A Spacetime

**Summary for the Chapter:**

> From the Big Bang to the Formation of the Earth

Fantastic colors and shapes pass before your eyes as you sit inside the time machine with Peridot, who is currently sitting back and sharing the sights with you.

“We’ll be heading for the Big Bang in a few minutes. Now, you’re probably wondering ‘Peridot, if we were really going to the beginning of everything, why don’t we start before the Big Bang?’ See, here’s the thing: we know that Space and Time are linked together and we recognize that the two originated with the Big Bang itself. Therefore, there can’t be a ‘before the Big Bang’ because Time didn’t exist yet! Who knows what was going on, but that’s something that doesn’t concern us right now.” Peridot explains, “the Big Bang is the start of the universe as we know it, and I could go on about the physics behind that, but I’ll spare you the details. Even the most experienced of Gem scientists don’t have all the answers, and they’ve been cracking at this for tens of thousands of years before your species knew what a ‘universe’ even was.”

The timer blinks once, reading:

_13.8 Billion Years Ago_

Peridot clicks at it and the time machine stops moving. 

At that very moment, the vehicle shakes violently and the two of you are left in a sudden haze as the view outside the holoscreen becomes next to impossible to make out. It almost hurts, and Peridot’s form flickers in and out a few times! After about three minutes of this, you two manage to regain your composure.

“Oh stars that was weirder than I pictured.” Peridot shakes her head, attempting to look outside the holoscreen but quickly shielding her eyes. “Don’t look out the screen! Just focus on me.” 

You resist the urge to look, but soon shift your eyes on Peridot. “It is blindingly bright out there, you don’t want to damage your eyes.” Her mood quickly picks up, “but how cool was that?! We’ve only been here for something like three minutes, but already the cosmos has rapidly expanded and given rise to spacetime! In just the first second after the Big Bang, the great forces of our universe - gravity, electromagnetism, strong- and weak-force - have come into existence! These are the fundamentals that directly affect matter and energy, which themselves have also burst forth from the Big Bang! All the matter and energy that will ever be!”

Peridot pulls out a small screen from the chest to illustrate her point. “As you can see here, within the first second of the Big Bang, there was matter and antimatter, quarks and antiquarks and such. Basically, the building blocks of all matter and energy had their opposite counterparts. When pitted against each other in the fantastic heat and density of the Big Bang’s expansion, the anti-neighbors were annihilated! After the first three minutes of the Big Bang, the remnants of these particle-wars, protons, neutrons, and electrons, are now floating around in space. It will take about 380,000 years before these particles come together to form proper atoms.”

Taking care to dim the holoscreen to protect them from the intense light, Peridot punches in a new date on the screen. “Let’s jump ahead 200 million years. The cosmos should be much more bearable to the eyes.”

With that, the time machine vanishes from the hot, dense early universe.

…

_13.6 Billion Years Ago_

The time machine appears in a vast plane of existence, and everything is much darker than before. So dark in fact, that save for the lights inside the machine, you’re not able to see anything beyond the holoscreen. It’s so dark you don’t believe it at first.

“Ugh, this isn’t any better. This is, like, the complete opposite of our previous situation.” Peridot rolls her eyes, only to give a reassuring smile at you afterwards. “Don’t sweat, we’ll have a much better view soon.”

Peridot gestures outside the holoscreen. “The first atoms to form from the Big Bang were hydrogen, helium, lithium, and beryllium, and… well, that’s all the universe pretty much was for a long time. Save for some additional matter that your Earth scientists have called ‘dark matter’, that is. We don’t really know what dark matter is, if it exists at all. We know that there’s something throughout the cosmos that interacts with other matter and affects it in certain ways, but because it doesn’t emit light or radiation or anything like that, we can’t observe it directly. Dark matter is just a convenient name! This mysterious substance is quite plentiful: something like 85% of the universe is made of it.”

You observe what appear to be gradually glowing cloudy-ribbons stretching out across your field of view. They’re brightening before your eyes.

“Whatever it is, dark matter seems to have been important for the formation of stars and galaxies. As it interacted with the atoms, gravity cemented them closer and closer together. The atoms began to fuse into each other and after enough time these fusions created very large spherical masses that acted as giant nuclear fusion reactors. The energy released from these spheres radiated bright light. And, presto, that’s how the first stars were made!” 

Sure enough, space started to fill with twinkling lights. Peridot flies the time machine a little closer to one of them, a massive ball of plasma, but not too close due to the radiation.

“Ahh, light returns to the cosmos! But don’t get too familiar with these stars, they’re not going to be around for long. I’m going to fast forward a few million years and you’ll see what I mean.”

Clicking a special dial on the holoscreen, the view outside begins to change rapidly as more and more stars form in the blink of an eye. A few of these stars, including the nearest one you’re parked at, begin to collapse into smaller and smaller spheres. Peridot slows down the speed to a rapid halt, and the shrinking star begins to shoot out gas. 

“Stand back!” Peridot scoots the time machine a good ways backward, just in time as the dying star explodes into a supernova. One by one, other stars follow, like an interstellar fireworks display.

“While the deaths of these early stars - the first generation - might seem sad at first, they were monumental in the course of history! Because these supernova explosions were powerful enough to forge different types of fusion reactions, which created brand new elements! The remaining 22 elements of your Earth’s Periodic Table for forged from the deaths of the first stars and spewed outwards all across space: from carbon, nitrogen, and oxygen, aluminum, silicon, and phosphorus, all the way to iron. These are the most basic elements found in the cosmos today, and form the foundations of all that you humans know. The air you breathe, the water you drink, the plants and animals that surround you, the very make-up of your body, was all thanks to these stars! So I think a thank you is in order.”

Grinning as you roll your eyes, Peridot punches some new time-coordinates into the holoscreen and heads off forward in time. 

…

_4.5 Billion Years Ago_

The time machine reappears in a cosmos that looks much fuller. There is an increased abundance of stars and colorful nebulae, as well as faint traces of other galaxies beyond your field of view. Peridot checks her holoscreen before grabbing a juice-pouch from the chest.

“I hope you don’t mind, but I’ve gone ahead and jumped some nine billion years into the future. The wonders of the universe never cease to amaze, but the timescales are just too long and I don’t want to bore you. I’m not boring you am I?” Peridot turns to you, frowning slightly. You shake your head ‘no’.

She smiles. “Glad to hear. Just to catch up… newer generations of stars were born from the remains of the previous ones, and many of the supernovae formed from the deaths of the later stars gave rise to even more elements! Things like nickel, copper, zinc, silver, gold (which are familiar metals on Earth), and all the way up to uranium. Basically the universe was now composed of 92 different elements, all able to form brand new stuff! After another period of 200 million years from the first generation stars, there was enough dust and gas in the cosmos to form the first proper galaxies. Given that galaxies are composed of many different types of stars and gaseous clouds formed in successive stages, we can’t really put a specific ‘birth date’ on them. As far as we know, your home galaxy, the Milky Way, is probably almost as old as the cosmos itself!”

Peridot takes the time machine and sails headfirst into the spiral arms of the Milky Way, passing star clusters and nebulae. “While it would be proper to talk about the histories of the different galaxies, stars, and planets, Homeworld included, you humans seem to care about your own home, so we’ll just stick inside the Milky Way.” Peridot places a finger to her lips. “Actually, come to think of it, we’d be here a while just talking about Homeworld’s history. And… there’s some funky stuff that happened there let me tell you.” Peridot shudders, before giving you a stern look. “And no, I won’t be giving you backstory spoilers to all my fellow Homeworld gems! Where did Pearl come from if she wasn’t White Diamond’s pearl? I’m not telling! SO DON’T ASK! My time machine, my rules.” 

You zoom in to what appears to be a giant disk of interstellar gas and dust, with a newborn star at its center surrounded by slowly-forming spheres of various sizes. “This should look familiar to you: it’s your solar system. The Sun had formed at about this time - 4.56 billion years ago - and the rest of the planets followed not long afterward. As you can see, this expansive disk of gas, dust, and ice surrounding the baby Sun has already begun the process of accretion. That’s how planets are made: small particles collide with other small particles, and those bigger particles seek out bigger and bigger ones, and next thing you know entire worlds are being sculpted!”

Peridot takes the ship and zooms in on the third most world from the Sun, still forming as meteors and other clumps of rock smack into it. Its surface is pot-marked by bright orange and white flashes. It’s a molten world. 

“Ahh, home sweet home. Welcome to Earth.” Peridot grins, gesturing at the proto-planet. “Earth is a rocky planet, formed from different types of metals. Because the Sun continuously sends out strong solar winds, many of the lighter elements, like hydrogen and helium, were blasted into the outer reaches of the Solar System, where the temperature was much colder. The planets that formed there were made of ice and methane, with thick atmospheres of hydrogen and helium. You know them as the gas giants.”

Peridot pulls out a small tablet and holds it up to you. Projected on the screen is a diagram of the Earth and its layers. “Originally, the different layers of the Earth’s interior - you know, the crust, mantle, and core - didn’t exist! The young Earth was just a mass of jumbled minerals collected by its gravitational field. It would take some 500 million years for the densest minerals like iron and nickel to sink down towards the center of the planet, and the lighter minerals like silicon to float upwards to the surface. And a core composed mostly of iron means that Earth gets to have a magnetic field! It’s a shield made of electric currents that surrounds the entire planet! That’s why the surface isn’t fried to a crisp by deadly solar radiation, so, you know, that’s good.” 

The time machine begins sounding a sharp alarm as the lights inside twinkle in different shades of red. Peridot sets the tablet down and checks the stats on the holoscreen. “Whuh oh! Don’t be alarmed, but we gotta get out of the way fast!” You look around the inside of the machine before squinting your eyes outside, struggling to see any sign of danger. 

“Hang on!” Peridot jerks the time machine as far as possible from the Earth. You still have trouble seeing anything. “You can’t see that?! Look over there!” Peridot points and immediately you tense up as a giant mass of molten minerals comes barreling towards the Earth! The time machine just barely misses the rapidly moving sphere as it collides with the planet’s surface. An immense explosion erupts from the collision as vast particles shoot out from all directions, some of them hitting the sides of the time machine, causing it to shake about. “Whoa whoa whoa, still too close! But I can’t do anything about that! Just keep calm!” Peridot exclaims, as the two of you hug each other for protection. After several minutes, the bombardment ceases, and the two of you pull apart, with Peridot peering towards the holoscreen. 

“Yipes! That would have been really bad for us!” Peridot turns off the alarm and the lights dim back to their normal settings. “That my friend, was the origin of your planet’s moon! Why does it seem like all space births are either very slow or very quick and violent?”

You look out the holoscreen to see that an enormous chunk has been ripped on the Earth’s molten surface, while an enormous cloud of rocky and dusty debris encircles it. “That baby planet really did a number on the young Earth, we’re gonna have to fast forward a bit to get the full effect.” Peridot turns the special dial and you watch as the giant mess of particles quickly orbits around the Earth, almost like the rings of Saturn. The huge gash becomes fully smoothed out as gravity reworks the planet, and before long a small ball of material begins to orbit inside the ring of dust and rock. As Peridot winds down the speed, all that is left orbiting the Earth is a small molten orb, the Moon. 

“There we go! Isn’t that nice? Now the Earth has a partner… and what a great partner the Moon is! Not only would the Moon push and pull at the planet’s surface, creating tides, but that initial impact alone seems to be the reason the Earth is tilted 23 degrees, setting the foundations of what will become the seasons! The Moon started out very near to the Earth’s surface, so a day on Earth right now only lasts a few hours, but the Moon has already started its very long process of moving away from the Earth, hence your Earth-days lasting 24 hours.”

Peridot adjusts the holoscreen settings and sets in a new date. “We’ll need to come back in several hundred million years in order to walk about properly. From here on out, we’re Earth-bound!” 

With a gleeful push of the button, the time machine disappears yet again.

…

_3.8 Billion Years Ago_

Your eyes adjust to an oddly familiar setting. The intense molten surface of the Earth has been replaced by a ashy-gray and black landscape of nearly hills and cliffs. Rocks of all sizes dot the area, and you turn the other way and spot the sandy seashore. The ocean doesn’t look very inviting from what you’re used to in Beach City: the water is a rich shade of reddish-black. Even the sky has an orange glow. You know it’s Earth, but it could also be some completely different planet altogether. 

Adjusting the brightness inside, Peridot reaches into the chest and pulls out a breathing-apparatus that looks suspiciously like a diving mask that’s been modified. “You’re gonna want to put this on. Gems can adjust themselves to nearly every planetary condition, but I’m not about to lose you so early on our adventure!” You take it and put it on with relative ease, securing it around your head. You give a thumbs up to Peridot, who shuts off the holoscreen and opens the window. You take her hand as she leads you to the outside.

“Ahh, feels good to stretch the legs. You holding up okay?” She asked, taking her hand back and holding her opposite one together. You nod your head. “Great! Welcome to Earth 3.8 billion years ago! Not exactly homey, but it’s home.”

Peridot walks around, stopping to pick up a rock. “When the Moon first formed, it was so close that its tidal pull stretched parts of the land nearly a mile into the air! This put a lot of energy on the young planet and kept its surface scalding hot. When it got further away from the Earth, the crust was finally able to cool and stabilize. There was still plenty of volcanic activity going on, as you can see on the horizon…” She gestures to your right: indeed there is a warm glow in the distance. “... but now the Earth had proper land, and with proper land came the potential for oceans of liquid water!”

Peridot walks up to the seashore and chucks the rock in such a way as to make it skip across the water. “Heheh, Amethyst taught me that. The oceans formed from water vater that had escaped from the solid crust and condensed in the air. This rained down in a torrential storm that lasted until most of the water vapor was used up, creating the ocean and thus starting the water cycle! Additional water may have come from comet impacts, since comets are part ice.”

Pointing to the air, Peridot gestures wildly, “the Earth’s atmosphere was formed by trial and error. Its original atmosphere was mostly hydrogen and helium, you know, the lighter elements left over from the birth of the Sun. But because the magnetic field hadn’t formed yet, that atmosphere was blown away by solar winds. The air you see right now is a second, heavily guarded atmosphere, made of nearly all the stuff it’s composed of in the present day: nitrogen, water vapor, carbon dioxide, methane… only oxygen was missing, but that’s a story for later.”

You walk with Peridot for a little bit as you leave the time machine behind. Eventually she finds a comfy boulder overlooking the seashore. Laying down on it, she gestures you to sit beside her. There’s a calmness in the air as you look towards the illuminating volcanic horizon of yellows and oranges. 

Peridot closes her eyes. “What a paradox. It’s so peaceful here, but just across the sea the Earth is bleeding out. Volcanic eruptions churning and shaping the land into new forms. Even the ocean is helping out, because with an ocean of liquid water comes erosion. Rocks get carved and sculpted, and you get things like sand. As we speak, plate tectonics has only just begun, splitting the crust into chucks and kickstarting a process that will further shape the land and sea. So much violence… and yet… it’s a nurturing violence. A reassuring violence. It’s like the planet is saying, ‘hey, don’t worry about me, I’m just doing what I do.’ Wow.”

You recline your arms behind your head as you close your eyes too. The two of you chill there for a while. 

Peridot opens her eyes and turns to you. “Let’s rest a little longer. When we get back to the time machine, you’re in for a treat. You’ll get to meet your very first ancestors.”

…

**_To Be Continued!_ **

**Notes for the Chapter:**

> Special thanks to Stephen Hawking and Leonard Mlodinow's "A Briefer History of Time" (2005) and DK's Multi-Authored "Big History" (2016) for information.


	3. Get A Life

**Summary for the Chapter:**

> From the Origin of Life to the First Land Plants

_3.8 Billion Years Ago_

After a little nap along the margins of the primeval shoreline, you walk with Peridot back to the time machine. She talks as she sets up everything. “As far as organic life on the planet Earth is concerned, we haven’t the foggiest clue how it got started. Your scientists have been hard at work observing, hypothesizing, and testing anything and everything related to this mystery, but at the moment we can’t say anything definitive. That being said, they have been amassing and connecting all sorts of puzzle pieces to the question of organic life’s origins, and for right now, we have some… highly likely scenarios that we can explore. But to do that, we gotta get smaller!” 

Opening up a new section of the holoscreen, Peridot places a finger along what looks like a computer scroll bar and pulls downward. Next thing you know, the view outside the window appears to be growing tremendously. Taking a cue from Peridot’s words, you realize that she’s shrinking the time machine! 

As you reach microscopic size, Peridot takes the pod and flies it right into the seashore. You dive down, deeper and deeper, darker and darker, until it’s nearly impossible to make anything out. After several minutes of travel, Peridot slows the time machine to a halt and flips on some headlights. You see what appears to be several large castles of rough-yet-polished stone. The water surrounding the pod is very still, but you feel the warmth radiating from these rocky structures. All around you are millions of small molecules, swimming around and or floating like suspended snowflakes. 

“Organic life on Earth is made up of cells, which are these little tiny bags of matter that perform all sorts of functions, mainly keeping the organics alive. Given what we know about Earth life, the first organics were single-celled, but there’s a very long road to get to something as complex as a cell. Scientists call this period of development ‘abiogenesis’: before life appeared.” 

Peridot drives the pod up to some early microbes. “These early bacteria can help you understand. By this time, 3.8 billion years ago, life seems to have already finished abiogenesis, and you can see all the end-results clearly with these little guys.” She focuses the headlights directly on one of the bacteria, giving a good outline of all its internal anatomy. “Cells are made of organic molecules, which are chains of atoms. Our friend carbon, which we met after its creation from the first generation of stars, was the most important of these linked atoms, because it’s the only one that can readily bond with other atoms to form organic molecules in the first place. And these chains can link even further together to form larger ‘macro’-molecules, like sugars, amino acids, phosphates, and nucleotides.”

Peridot points to the center of the bacterium, drawing your attention to the large stringy mass at the center of it. “Moving a step further, nucleotides, phosphates, and sugars combined make up the structure of DNA and RNA. It’s thanks to these molecules that organics have the necessary blueprints to reproduce and make more of themselves! Ahh the miracle of life.” Peridot beams, before motioning the time machine back towards the stone castles. 

“I noticed you looking at those rocks. Those are alkaline hydrothermal vents. There are quite a few of them on your present-day Earth, deep in the oceans. Certain types of rocks from deep in the mantle interact with water inside the vents, causing it to heat up tremendously, after which it is exhaled through all those little holes along its surface. Thankfully, I’ve designed this time machine to be resistant to extreme temperatures, but I still can’t help but feel the warmth. My temperature gage tells me the water surrounding us is 190 degrees fahrenheit. Well, an oven is much hotter, but still. Yeesh.” 

The pod zooms down towards the hydrothermal vents and is quickly surrounded by all sorts of floating molecules. “Earth scientists suspect that vents like these provided the ideal conditions to foster the building of organic molecules and eventually the first living things. Living cells need a constant energy flow of carbon atoms to sustain themselves, and you get just that in environments like these.” 

Peridot notices some small wiggly molecules floating about and sticking to each other, and she takes the time machine closer to them. “Ooh! Look! Phospholipids! These little cuties are made up of two parts: a head that is attracted to water and a tail that despises water. As you can see, these molecules will often seek each other out in the right conditions and form little bubbles. All the heads made up the outer wall, and the tails form the inner wall. If we turn to the little bacteria we saw earlier…” and Peridot moves the pod back to them “... we can see the importance of this process in abiogenesis. The phospholipids would have provided a safe home for all these forming organic molecules, and with a few more alterations, the first cells arose!”

Now the time machine is moving away from the hydrothermal vents and slowly cruises along the ocean floor, passing by countless varieties of bacteria. “The last step towards proper organic life was the ability to reproduce. Having mentioned DNA and its coded instructions, but I should also mention that those phospholipid bubbles we saw have the ability to grow by adding new phospholipids from the environment. But after a certain size, the bubbles can’t get any bigger and they collapse down their middles, eventually splitting into two bubbles. You might see where I’m going with this. With DNA safely inside the proto-cells, copying itself as it does, there would come a point where the cell would need to split. This process would cause the DNA to replicate itself entirely, as would the rest of the cells component parts. Now, the DNA replication process isn’t always clear cut, and mistakes get made all the time. These little changes in the DNA code, what we call mutations, can have little to major consequences on how the cell functions. Once this process started in the early oceans, evolution could begin, and thus, organic life could truly call itself alive.”

Peridot sets a new date, “how exciting. Steven explained it to me best, ‘everything always changes here on Earth. Nothing is still.’ Evolution is a way that ensures that living things are always able to experiment and explore new possibilities. Organic life can be rigorously shaped by its environment, and shape its environment in turn. Certain ways of life can be so successful that they’re copied by different organics again and again. And sometimes the most insignificant mutations can have cascading effects! Let’s move forward and I’ll show you what I mean.”

…

_1.8 Billion Years Ago_

The time machine, still shrunk, reappears in the Earth’s ocean, but it’s still pitch dark around you. “Woops, I need to take us to the surface.” Peridot comments, and as she moves the pod upwards, you notice that the reddish-black water has become a rich blue. Near the surface, Peridot stops the machine, and you can see sunlight sparkling through the waves above.

“For nearly 850 million years after it developed, organic life was anaerobic. That means that they didn’t use oxygen in their daily functions. These bacteria and their relatives were able to survive just fine, all they had to do was eat the inorganic materials around them. But there was still a problem: even with a magnetic field protecting from solar winds, ultraviolet radiation was still an ever present danger to Earth life. The first life had to stay down very very deep in the oceans to keep themselves from dying.”

The pod is surrounded by all sorts of microscopic organisms. “As you can see around us, that’s no longer the case by now. And it’s all thanks to the power of photosynthesis! Check out these bacteria!” Peridot grins as she motions both of her hands towards some of the single-celled creatures, who had a green tint to them. “It’s a genius mutation: they take the energy from sunlight and use that to turn carbon dioxide and water into sugar, which gives the cell energy function! Not only that, but they release oxygen as a waste product. Remember the early atmosphere? All colored orange?”

You nod curiously, at which point Peridot jolts the time machine at the ocean surface. The sky has turned a familiar shade of light blue, and there are white fluffy clouds about. “All that oxygen had to go somewhere: the sky! Well… first it sank into the seafloor and rusted all the iron minerals there… but then it went to the sky! Earth’s earliest atmospheres had no oxygen, but they had a lot of harmful methane and ammonia. The ever increasing flow of oxygen displaced much of this stuff down to safer levels, and later formed a thick blanket around the planet that we call the ozone layer, keeping most of the ultraviolet light from reaching the surface. Isn’t that cool?! Organic life essentially changed the planet!”

Peridot took the time machine down into the ocean again. “All the anaerobic life that had previously been confined to the seas was able to reach higher and higher in the water until they covered the seas. Now that there was a ton of oxygen, some of the anaerobic life evolved into aerobic life, while the others had to find new environments to live. Evolution in action.”

The two of you admire all the different bacteria from the window, but after a while a large shadow starts to loom over you. Your eyes grow wide in confusion. Noticing this too, Peridot turns the pod and comes face-to-face with the looming maw of a much larger single-celled creature. 

“WAAHHHHHH!!” Peridot screams as the time machine is consumed completely! The creature swims along as the two of you are trapped inside a soft-gelatin mass of stuff. 

“Aww gross!” Peridot exclaimed, “... well… it’s not like we’re in any real danger anyway. Might as well take this situation as a convenience, since this organic represents a crucial part of my story.” Leaning back, Peridot continues, “all of the Earth’s life during the first 2 billion years was prokaryotic, meaning that their cells were relatively simplistic: mostly made of a mass of DNA at its center. But around this time, 1.8 billion years ago, the first eukaryotic organics evolved. This time, the cell was much more complex, with a nucleus at its center to house DNA, and multiple other ‘organelles’ that perform different tasks. You can see the nucleus inside our hungry eukaryotic friend here.” You’re able to make out the greenish sphere from beyond the window, along with some other more ovaline shapes alongside it, which you gesture to Peridot. 

Smiling, she places a hand on your shoulder. “Good eye! Those are mitochondria, which give eukaryotic cells energy. Do they look familiar to you?” You turn back, squinting at the globular ovals for good measure. “Kinda look like bacteria, don’t they? Well, you’d be right! It turns out that the mitochondria, one of the fundamental characteristics found in nearly all eukaryotic organisms, originated from free-swimming bacteria.”

Peridot pulls out her screen, “as our voracious host has demonstrated, many single-celled organics eat by completely encapsulating others. Now, usually, the prey are digested, but at sometime before 1.8 billion years ago, one of these single-celled creatures ate a smaller bacteria. Instead of digesting it, the two learned to live together: the bacteria providing the larger host with an easy energy supply, the host providing protection for the little one. Following the generations, this relationship remained strong until the two could no longer live without the other! Talk about the perfect fusion! Garnet would be proud.” Peridot chuckled happily, “from these emerged all eukaryotic organics on Earth, basically all of the most familiar kinds you know about, like plants, fungi, and animals, as well as other microbial things like amoebas.”

You feel the time machine shaking, which causes Peridot to groan. “Ugh… we’re humble travelers from the future and all we get as a ‘hello’ is stomach grumbles?! Where are this thing’s manners?! Let’s get out of here.” 

Peridot sets the timer again, and the time machine vanishes in a flash, leaving a very confused and upset eukaryote.

…

_740 Million Years Ago_

The time machine, now regular size, blinks into a drastically different landscape. There are enormous glaciers surrounding the pod, which has become partially submerged in a muddy snowbank. The cold is so intense that you feel the change inside the pod, and gusts of wind pound at the sides. The sky is intimidatingly cloudy. 

Seeing you shiver, Peridot wraps an arm around your body as her gemstone begins to glow. “This should help. My gem can radiate heat. We won’t be here for too long anyway, I just want to show you a very dramatic episode of Earth’s history.”

You feel the heat begin to work its magic and soon you’re snug as a bug. 

“The rise of oxygen in the atmosphere not only lowered the levels of harmful methane and ammonia, it also dropped carbon dioxide levels. Carbon dioxide is a greenhouse gas: it works like a blanket, trapping heat from the sun and keeping it on Earth, causing warming. So for the first few billion years, Earth was a toasty place. But with all this oxygen now crowding everything, the Earth’s climate began to cool. Add to that a many millions of years of great forests of photosynthesizing marine algae, releasing even more oxygen! It got so bad that - at least once - the entire planet became covered in snow and ice. That’s where we’re at right now: 740 million years ago, Snowball Earth.”

Peridot takes the controls and activates the pod’s walking legs. Taking a cruise across the snowy fields, you see small frozen streams but no sign of the ocean.

“This was a very difficult time for life. Because Snowball Earth formed so quickly, many organics didn’t have enough time to adapt to the changes, and they died off in huge numbers. That’s a trend that you’ll notice in the history of Earth life, as gradual changes in environmental conditions are much more manageable for living things to evolve with than sudden shifts like this. Those that survived were able to do so because they migrated to the furthest depths of the oceans, which were spared from the intense cold.”

Hearing a strong rumbling sound, you cock your head to the side. “I hear it too, let’s investigate.” Peridot motions the pod forwards as the legs sprint across the landscape, only stopping once it reaches the edge of a glacial cliff-face. In the distance is a massive volcano, erupting and spewing thick clouds of ash.

“Ah, of course.” Peridot comments, “Snowball Earth only ended because of a massive spike in volcanic activity. Volcanoes release carbon dioxide as waste products, and this change reduced the amount of oxygen and brought to Earth on a steady rise in temperatures. This melted all the glaciers and once again provided a planet that was safe for life to live on. Now the conditions were right for the next great change!”

…

_508 Million Years Ago_

The time machine appears at the surface of a vast lagoon, floating calmly in the water. The sun has just risen, and the sky is bathed in a calm pinkish-orange. You can definitely tell there is a change in the air, you feel it. 

“After Snowball Earth, animal life evolved and diversified into a myriad variety of forms. Animals, like most plants and fungi, are multicellular: made of many cells. Multicellular organics have been around for a billion years or more, some prokaryotic, others eukaryotic, but animals were unique in that they’re the only multicellular eukaryotes that move around by themselves.” 

Peridot takes the pod and descends below the depths, curving over the edge of a massive slope hundreds of feet high. “Be sure to take a good look, because life on Earth has gotten much more fascinating!” 

Going down about 320 feet, you finally reach the seafloor and your sight is treated to a spectacle of colorful and diverse animal life. Stalked forms, free-swimming forms, crawling forms, burrowing forms: each one is weirder than the last, just barely recognizable as anything you’ve seen at the beach or aquarium. Peridot shares your enthusiasm. 

“It’s awesome. Animals as far as the eye can see! This time is known as the Cambrian Period and it marks the time when organic life became much more abundant, much more complex, and actually visible to the naked eye. No need for shrinkage here!” Peridot, takes the pod and hovers over a grove of strange, bug-like animals that resemble rolly-pollies. “These hardy little critters are called trilobites, cousins of insects and spiders. During this time, they evolved and became super common, probably the most common animals around! What makes them and many other animals so special is that they were the first organics to develop hard parts to their bodies. What we call skeletons!”

Peridot pushes a button on the holoscreen, which sends a small grabbing arm outwards. The arm picks up a trilobite as the others swarm away from it. Gently, the arm brings the squirming animal close to the window. “Pardon me little buddy.” Peridot sheepishly smiles, “I need you for a second.” 

She gestures you to come closer to the window. “The first animals, like all early organics, had soft bodies that were often delicate. The first animals to evolve hard parts were worms that incorporated neighboring minerals into their growth, what we call biomineralization. These worms developed sharp teeth that they used to better grasp their squishy prey. As an evolutionary response, these prey animals all took to using biomineralization for themselves, creating sharp spines or hard shells for protection, or even stiffening rods to support themselves on the seabed. Before long, much of the animal kingdom had hard parts of some sort, leading to the evolution of major animal groups like the mollusks and the arthropods, the latter being the group that organics like this little trilobite belong to.”

Peridot makes the arm release the little animal, which wiggles around in shock before swimming back down to the seafloor and burying itself. 

“Many of the animals you see here belong to groups that have survived and diversified in the present day. But there are others that have left no living descendants today. Even if we know who their closest relatives are, they still defy expectations. Like, check out this one!” Peridot motions towards a great free-swimming animal that had been circling the area for a while, hunting for prey. It has two bulbous eyes on its head, tipped below with two grabbing arms lined with spines. The body is long with undulating fins all along its sides. 

“Talk about alien… of course, I would know. Nehehe! This is _Anomalocaris_ , and it is abnormal! It’s a great predator, using those spiny arms to grab smaller, softer animals and bringing them to a circular tooth-lined mouth under its face. Not a way I’d want to go. Look at those eyes! Eyes are another big adaptation that became fully realized during the Cambrian. Originally developing as light-sensing spots, over time several lineages of organics modified their eyes by creating little depressions in their faces which allowed them to sense direction. Some added a pinhole to give proper image processing, and eventually lenses for clearer sight. You know, the first gems had eyes… we didn’t have to go through all of that.”

You shrug your shoulders, which causes Peridot to giggle, “what can I say? Earth life is but one of many!” 

After giggling a little longer, Peridot suddenly jolts upright, flailing her arms. “OH OH OH I ALMOST FORGOT!! You’d probably really appreciate this.” Taking the controls, Peridot scans the seafloor for a very particular organic, and after a few minutes she finds it.

“Ta da!” She gestures comically out the window, to which you creep up and give a good look outside. All you see is a small worm-like animal with a notable fin along its entire body and a head tipped with antennae and feelers. You’re not particularly impressed. Noticing this, Peridot does a double take. “Are you serious? This is not the reaction I was expecting! You should be gasping in shock!” You give her a deadpan look. “Ugh. I guess I do have to explain everything… Okay. That little animal is called _Pikaia_. What makes it special is that it was one of the first chordates, the group that includes vertebrate life. You know… fish and reptiles and mammals… including humans like you?”

You nod your head, giving a small “ah” with your voice as you understand. Rolling her eyes, Peridot crosses her arms. “Wow, thanks. Anyway… chordates became unique among animal life in that they developed a stiffened rod along the inside of their bodies called a notochord, which protects the nerve cord. This rod is made of cartilage, which is a hard substance that makes up many parts of your body, like your nose and ears. This was another byproduct of the hardening of animal bodies during the Cambrian. Over time, this notochord was toughened by an extra layer of true bone called vertebrae. That’s why you’re a vertebrate.” 

Peridot begins setting the timer. “The Cambrian Period would not be the only time in your planet’s history when life diversified into new forms. There were always changes taking place on Earth that set up new obstacles, and organic life either adapted and survived or perished into extinction.”

…

_460 Million Years Ago_

Still surrounded by the ocean, the time machine now resided above a must vaster expanse of seafloor. The small bed of unique organisms has been almost completely changed as great reefs of corals sway and grow in the gentle waters. There are forests of sea lilies (strange relatives of the starfish that look like underwater palm trees) and a variety of snails and clams in-between the corals. There are still plenty of trilobites around too. In the open ocean above you can see jellyfish and other creatures swimming and floating about. In all, it’s a much different scene. 

“We’ve now jumped to another period in Earth’s history, the Ordovician. A world of tropical oceans, this time saw the rise of brand new ecological niches… those are the roles that organics fill in their environment, be that predator, prey, scavenger, you name it! Animals began to swim further and further out to sea, away from the seafloor, while others started digging deeper and deeper burrows. In essence, the Ordovician set up the marine ecosystem that was to remain nearly unchanged for the next 233 million years!”

Peridot begins to steer the time machine upwards, but accidentally bumps into a giant orthocone (a giant type of cephalopod, with a long vertical shell, that hangs suspended in the water like an icicle). “Whoops! Excuse me!” Peridot shouts, before driving on.

“While the oceans remained crowded with life, it took a little longer for anything to gain a significant foothold on land.” Peridot explains as the time machine surfaces, gradually moving along until it reaches the coastline. “Until the ozone layer were properly established, nothing could really live on land at all! And until 460 million years ago, it was almost as barren as it was 3.8 billion years ago. Talk about boring.”

The pod rests on a sandy beach, the legs extended out as support hooks. Handing you the breathing mask, Peridot leads you outside once again. The beach, as you expected from her explanation, wasn’t as empty as it was before. You can clearly make out fields of green, yellow, and brown alongside small rivers going outwards onto the land. You follow Peridot as she guides you to the freshwater stream, taking a seat next to her as she continues. 

“Plants, like all other organics, evolved in the oceans, but the first land plants developed from species that moved into freshwater. These plants were able to support themselves on dry land because they either had flattened leaves (like liverworts) or because they used root-like structures to secure themselves to the ground (like mosses).” After Peridot’s explanation, some of the mosses begin sending out very small clumps from their leaves which float in the wind. You back up slightly to prevent them from getting on you. “Hehe, don’t get too close! Early land plants, like mosses in the present day, reproduced with spores. These are tiny microscopic cells that float in the wind and, when they land, grow into copies of their parents. But spores only work in wet places, so the first land plants were confined to the moist places by the rivers and streams.”

Looking around and breathing in, Peridot sighs contently. “Even with all this green, the land is still pretty much barren. There isn’t enough food for animals yet, but the first land plants wouldn’t be alone for long. You notice how the ground where the plants are growing is really rich with dirt? That’s the first soil, created by the first fungi to join plants on land! When I first started really learning about Earth, I thought that fungi, like mushrooms, were plants, but Steven’s friend Connie explained that fungi belonged to their own group of life. They’re decomposers, relying on dead organic matter for food. As the early plants began to die, they left behind a buffet of food, and so fungi began to colonize the land too. When they feasted on the plants, their bodies churned the ground, and created soil. And, if you’re like me and you love gardening, you know that soil is a big plus for providing plant nutrients. Here, come inside the time machine and I’ll show you!”

Back inside, Peridot clicked the special fast-forward dial. This was the first time she used while on the planet Earth, and the view was absolutely spectacular. Day turned to night and back within milliseconds as the landscape changed before your eyes. Mountains rose and fell, canyons widened and shrunk, and gradually the small mossy patches gave way to much denser patches of foliage. Peridot stops fast-forwarding, and opens the time machine again.

“We’re now 420 million years ago, hitting another milestone in land plant evolution.” Peridot runs out and plucks one of the plants and hands it to you. It’s a strange thing between your fingers: a two-inch long branching patch of leafless, woodless stalks tipped at the ends by rounded points. “That tiny plant is called _Cooksonia_ , and it’s one of the first plants with vascular tissue. These tissues functioned as a series of strengthened, interconnected tubes that acted like the veins in your body, here providing a delivery system for water to reach every corner of the plant. This was a very efficient system, and that, coupled with the first true roots, allowed plants like these to move much further out into the land.”

You feel something crawling on your foot, and you quickly flinch your foot in alarm, sending whatever it was into the foliage. “Hey! Careful!” Peridot shouts, before running towards the plants and picking up the launched animal. “It was only a millipede.” she comments, letting the multi-legged animal crawl along her fingers. “Now that there was plenty of food and shelter thanks to the plants, animals were now able to make the first steps onto land. It was arthropods like these that did it first. The hard shells that they developed during the Cambrian proved very good for landlife, their stiff, articulated legs providing support for their bodies.”

Gently, she let the millipede back into the small forest. “Once plant-eating arthropods started living on land, it wasn’t long before meat-eating ones followed them. Okay… you’re actually gonna want to take a step back.” 

Peridot walks beside you and carefully moves you backward as a couple of scorpions begin marching along where you stood. “Well, would you look at that, we now have fully functioning ecosystems in the sea _and_ on the land! And it only took, what, 3.3 billion years? HA! Homeworld had already conquered all the arms of its galaxy by then.”

“Here,” Peridot begins leading you back inside, “let’s fast-forward one more time and see how the forest changes. You’re gonna love this!” 

Sure enough, as the dial is switched, the Earth transforms dynamically. But your view of the distant mountains becomes quickly obscured as great trees begin sprouting up all around, until before long the time machine is surrounded by plants, bordered on one side by a shallow lake.

Opening the hatch, Peridot jumps out and cackles into the air. “HAHA! I’m amazing.” She turns to you, hopping in place, “isn’t this cool?! 380 million years ago and the world finally has trees! And ferns! Plants with actual leaves! Ahh, Lapis would have loved this.” 

Peridot walks around admiring everything, and you can’t help but join her. It is certainly much more appealing than those moss patches, pioneering as they were. “Some of the smaller trees you see here have developed a special mutation that has completely changed their reproductive habits. Seeds.” Peridot pulls on the branch of one of these plants and brings it closer to your view. “Unlike spores, seeds are encased in hard shells with food storage for the little plant embryo inside. Seeds were made when land plants began dividing their spores into two different structures: the female spores staying attached to the parent plant while the male spores (called pollen) were sent out from the parent plant to fertilize a different plant. Once connected to the female spore, the pollen fused to it and formed an egg that grew into a seed! All that was left was for the seed to fall, be planted to the ground, and a new plant is made! Earth fusion is so unique from Gem fusion, but special all the same!” Peridot smiled.

Leaving that plant for another one, Peridot ran her hand along the trunk, gesturing you to do the same. As you feel the plant, you notice a familiar toughness to your touch. It’s wood. “Some vascular land plants began using wood to support their bodies, and this allowed them to grow to immense heights, hence all these trees you see around you. And this allowed them to move even farther into the land!”

Surprisingly, the forest is still very quiet, and you cup your hand to your ears to try to pick up anything at all. Peridot notices this: “ahh, don’t bother. There’s nothing to make noises yet. Animal life has flourished on land quite a bit, but nothing that’s too chatty. But then again, a conversation with a mite, spider, or snail probably wouldn’t be too engaging anyway. All the real action is taking place along the waterways! Come on!”

…

**_To Be Continued!_ **

**Notes for the Chapter:**

> Special thanks to Robert Hazen's "The Story of Earth" (2012), Nick Lane's "The Vital Question" (2015), Firefly's Multi-Authored "Evolution: The Whole Story" (2015), and Dr. Thomas Holtz's Online UMD GEOL 102 "Historical Geology" Lecture Notes for information.


	4. The Brontosaurs and The Bees

**Summary for the Chapter:**

> From the Evolution of Land Vertebrates to the Extinction of the Non-Avian Dinosaurs

_380 Million Years Ago_

Having fast-forwarded time 80 million years to the Devonian Period, Peridot takes you by the edge of a large river, populated from shore to shore by ferns, horsetails, and great trees. The current is calm, but still moving at a noticeable pace. 

“Since we last left our aquatic friend _Pikaia_ back in the Cambrian,” Peridot begins, “fishes have undergone quite a number of important changes and diversified into a few distinct groups. Starting with the stiffened notochord, fishes grew entire skeletons of bone and some even started coating their bodies with tough armor. The descendants of these earliest fishes include the lampreys of the present day, which are these blood-sucking noodle things that give me the creeps.” Peridot shivers, before taking a stick and drawing along the ground as she talks, illustrating the evolution of fish.

“Later fishes developed jaws by modifying their gill arches into something that could open and close, allowing them to take in more water so they could breathe better. It was later on that this jaw was equipped with teeth, and so these animals were able to hunt for their meals. From these fishes came things like sharks and stingrays.” Peridot draws accordingly. “And that takes us to where we are now, 380 million years in the Devonian! Fishes have since given rise to two major lineages: the ray-finned fishes - basically most types of fish you can think of, like tuna, salmon, and perch - and the lobe-finned fishes, which are what we’re going to see now!” 

Motioning towards the water, Peridot urges you to peer closely into the water. You make out a long, slender form in the water, rather large, like the length of a broom. Peridot pulls out a small cylindrical device from her gem, “you might want to stand back, I’ve only tested this thing on Pumpkin.” You take a few steps backward as she fires a laser from the device, at which point the large freshwater animal is hauled from the water. Gaping its mouth, the animal wiggles around and flaps its tail about frantically. “Easy! Easy!” Peridot yelps, before pressing a small button on the device, which sends out a small tingle that calms the animal down. 

“Phew! Hehe, I’m a genius.” Peridot giggles, before turning towards you. “This, my friend, is called _Tiktaalik_. It’s one of those lobe-finned fishes I was telling you about. See, the thing that distinguishes the lobe-fins from the ray-fins is… well… in their name! Here, take a look.” Peridot walks up to the fish, the laser from the device still keeping it still, and holds up one of its fins. “Notice how fleshy the limb is? That’s because there’s a little arm in there, with a wrist and tiny digits and everything! As you almost certainly know, ray-finned fishes have a ‘ray’ of spines as their fins, which helps them out in open waters. But lobe-finned fishes originally lived in freshwater areas where there were tons of rocks and water plants in the way, so they used their fleshy arm-fins to creep around in the water or push away the plants. So when some species began making small journeys out of the water in search of food, they already had limbs with decent strength to help them move!”

Peridot lets the fin down, before moving her hand along the length of the _Tiktaalik_ ’s body. “Originally, fishes had a sort of air-sac in their bodies that helped them breathe along with their gills. The ray-finned fishes turned this organ into a swim-bladder, which stops them from sinking as they swim, while the lobe-finned fishes modified it into true lungs. So an animal like _Tiktaalik_ was not only able to collect oxygen from the water with gills, it could also breathe in air on the surface. In water and on land! That’s living a double life!”

Peridot gently places the animal over the water before turning off the device. The _Tiktaalik_ crashes into the water with a loud “SLAP!” as water splashes all over Peridot. Grumbling, she uses the heat from her gem to dry off. “I’m sure I deserved that…” 

Once finishes, she begins leading you back to the time machine. “Over the next few million years, these lobe-finned fishes will only get better and better and moving outside the water, but they would still remain attached their freshwater homes for all of their basic survival needs, like reproducing. It’s through baby-steps like this that the first land vertebrates evolved. Notice how fishes like our _Tiktaalik_ didn’t evolve their fleshy limbs or their lungs because they started living on land: they were already using them for other things. That happens a lot over the evolution of life: the features that we see on organics living on Earth in the present day usually evolved in completely different contexts before they were repurposed for other things. It’s pretty neat, don’t you think?”

You nod with a small smile as the both of you enter the time machine. Peridot sets new coordinates. “Let’s go see some end-results of this gradual process, in person!”

…

_300 Million Years Ago_

The time machine appears in yet another woodland, but this time the feeling is much different. Exiting the pod, you notice that the trees have gotten much MUCH taller, so much so that you can’t even make out the sky. The vegetation is very dense all around you, and you nearly cling to Peridot as a strong buzzing sound comes closer and closer to you, accompanied by a chorus of chirps and squeaks.

“Hey friend, take it easy, I got you.” Peridot smiles as she holds your hand, “welcome to the Carboniferous! Nearly all the world is forest! As you can tell, land plants have really taken off, and have supported a much larger terrestrial ecosystem than ever before. All that noise you hear around you are some of the many species of insects that have evolved since the Devonian. Including that guy! Incoming!” 

You both duck as the loud buzzing emanates from an enormous insect flying by, with a wingspan that looks similar to a hawk. Peridot’s eyes sparkle as the looks after it, “oooh! That’s a griffinfly. It’s a distant relative of the dragonflies, but a lot bigger clearly!” 

More fly by the two of you as you steer clear of the wings, “because there are so many plants around the planet, the levels of oxygen in the atmosphere have risen exponentially! Insects and other arthropods rely on oxygen for their growth, and so much of the bugs you see around us have evolved to larger sizes. This is about as large as insects and their kind will ever get.” 

“Speaking of animals,” Peridot looks over her shoulder before grinning and pulling you along, “during the Carboniferous the lobe-finned fishes had given rise to the first tetrapods, including the giant amphibians you see before you!” 

Peridot has pulled you to a grove of ferns, which she pulls aside so you can get a safe view of some truly impressive amphibians in a lagoon. They’re very crocodile-like with wide, flat heads, long bodies, and short, stout limbs. They’re all just resting against each other, to which you sigh gratefully, as you also noticed the rows of sharp teeth lining their jaws.

“Tetrapods are the group that encompasses all of the land-living, four-limbed vertebrates and their descendants. So every amphibian, reptile, bird, and mammal you know evolved from animals like these. But these early tetrapods, comfortable as they are walking on land, still relied on the water to lay their eggs. That won’t be the case for long, though. Come on! Let’s see if I can find a nest.”

Returning inside the time machine, Peridot takes the controls and skirts around the forest as carefully as she can, occasionally swatting through a branch or two. Finally, she stops and gently lowers the pod just enough so you can see a small nest cavity inside the log of a tree. The parent is nowhere to be seen.

“Steven’s let me try eggs before… they were pretty tasty, but when he told me about where eggs came from… I didn’t really feel like eating them anymore. But you gotta give them credit! Hard-shelled eggs were one of the last major evolutionary developments that finally broke the ties keeping tetrapods to the freshwater environment. While early tetrapods, and one of their descendant groups the amphibians, used eggs to store their embryos, they were soft, gelatinous things that needed to be in water to survive. The adaptation for hard-shelled eggs allowed water to be stored inside the egg, still there to keep the embryo alive. For the tetrapods that laid these eggs, called amniotes, this was a way to protect their young from the dangers of aquatic predators. They could now live further and further away from the rivers and streams, and become proper land living animals.” 

Peridot began to focus her attention more on the log than the eggs, as her mind clicked. “Before we leave the Carboniferous, I should mention something very crucial you’re gonna want to keep in mind.” She takes the ship and cruises across the forest. “From the time that trees started producing it, wood has been a valuable adaptation for sustaining the longevity of the plants who have it. In these times, there were no organics that could digest wood, so there was nothing to decompose it when the tree finally died. With every passing year, these trees died and sank into the ground, where the heat and pressures of the Earth’s movement would eventually turn them into a type of rock called coal. Now: when organics die and decompose, all the carbon that is stored in their bodies rises away into the air, waiting to be captured by photosynthesizing plants. But with nothing here to eat all this wood, the carbon atoms are left stuck inside the coal where they’d be buried for millions of years, away from the recycling motion of the carbon cycle.” Peridot scratches her nose as she sets new coordinates, “just… yeah, just remember that for later.”

…

_252 Million Years Ago_

The time machine is now floating in space yet again, hovering over the primeval Earth. You watch with Peridot as all of the continents appear collected together in one enormous landmass.

“The continents are always moving. So there are some times in prehistory when they’re all separated from each other, and others when they smash together, forming one supercontinent. During this time, the Permian, the last supercontinent formed (for the moment), called Pangaea. If you look, you can make out North America and Eurasia at the top, and South America, Africa, Australia, and Antarctica at the bottom. Yep, they’re all there!”

Peridot turns to you now, holding up her tablet and showing you pictures of different animals. “Land animals diversified greatly following the Carboniferous, particularly the amniotes, who now occupied a lot of different niches, some entirely new! There were burrowing animals, gliding animals, big predators, big prey, and even a few species that actually went back to living in the water! There’s no place like home, I guess.” 

Despite this, Peridot begins to frown, “but these times won’t last much longer. Here, let’s fast-forward a little bit, and pay close attention to where Siberia is.”

Indeed, you look towards the globe and watch as time passes by. Great patches of red emerge across Siberia, and before long thick clouds of smoke and ash bellow outwards from that region, eventually encompassing the entire planet in darkness. You take a second to process this, as Peridot stops fast-forwarding.

“That, my friend, is what mass extinction looks like. There have been a few in Earth’s history, affecting all organic lifeforms, but some more-so than others. During the end of the Permian, 252 million years ago, the biggest mass extinction event (for the moment) occurred. What you just witnessed was a large series of volcanic eruptions that spewed whole oceans of lava and threw up a thick blanket of choking carbon-dioxide-rich clouds. With so much carbon in the air, the temperature rose and heated the entire planet. Organic life on Earth starved and suffocated as whole ecosystems were destroyed: perhaps as much as 96% of all animals and plants died out. Those cute little trilobites we saw earlier? They all went extinct during this time, along with many other groups of fascinating organics.”

You look surprised as Peridot sets the coordinates up so soon. “Yeah, I just wanted to stop here real quick to set some context for the next part of our journey. It is sad, but I have to keep reminding myself that this isn’t a total loss. Organic life on Earth came so close to dying forever, but it didn’t! All the living things that we see in the present day are the direct descendants of those who survived through all the destruction. It’s part of the reason why being a Crystal Gem is so important to me: I get to help preserve the life on a planet that suffered through so much. Makes me wonder about all those successful colonies the Diamonds supervised. If they had been stopped in time, maybe some life could have survived and started anew? Who knows…”

…

_150 Million Years Ago_

It’s a new day. The sky is filled with white, puffy clouds as a gentle breeze blows through the air. Emerging from a large grove of ferns is an elderly man with a blue, button-up shirt and tan pants, his white hair flowing messily in the breeze. With an earnest smile, he speaks.

“I’m standing here amidst a world lost in time, inhabited by creatures beyond your imagination. Welcome to the Jurassic Period, during the age of-” he is interrupted as Peridot’s time machine appears nearby in a flash of light. The man is startled by the sight as he holds his hands to his face. 

Not hesitating, Peridot opens the time machine window and nearly sticks her whole body outside it. “HEY! What are you doing here Attenborough?!?!” she screams.

“I’m just informing our audience about the wonders of-”

“Nah nah nah, you got two whole stories. TWO! This is my turf. Beat it!” Peridot exclaims, slamming her fist on the wall of the pod.

“Hmph… very well. My apologies.” David Attenborough politely bowed his head and walked up to his time scooter. Starting the engine, he is teleported away from the scene.

Peridot crosses her arms, grumpily. “Errreeeyah!” she groans to herself. Noticing your confused look, she sheepishly turns back to you, blushing. “Ehh hehe. Forgive me. Anyway… welcome to the Jurassic Period! Just for frame of reference: Earth’s history is divided into different parts based upon the life and events uncovered from the rocks. There are Eras, which are divided into Periods, which can be further divided into Epochs, and so forth. Everything we just saw from the Cambrian onward belonged in the Paleozoic Era. Where we’re at now is called the Mesozoic, and we’re smack in the middle of it!”

Hopping out of the pod, Peridot takes a big whiff of the air, exhaling deeply and with excitement. “Ahh, nothing like a breath of humid, low-oxygen air to get you pumped! After the great dying at the end of the Permian, life rebounded! There were so many niches left open that the surviving organics were able to diversify into a number of unique forms. A few of which I’ve really been wanting to see! Come on!” 

Peridot takes your hand and leads you onwards through the brush. The plant life surrounding you is certainly much more removed from the coal forests of the Carboniferous. There are still plenty of ferns and horsetails, but now most of the trees are represented by conifers like ginkgos and monkey puzzles. It’s a very green world. 

Just cresting over a hill, Peridot stops and hops in excitement. “Hehehehe look! Look at that!” 

It’s honestly hard not to notice. Before you is an impressive herd of long-necked dinosaurs, slowly moving through a patch of trees and making short work of their foliage.

“The Mesozoic was the heyday of the reptiles, and none were more dominant than the dinosaurs! Even before I started reading up on them, I knew they had to be popular animals amongst you humans. Now I can certainly see why! This was the first time in Earth’s history that land animals gained such massive sizes, but of course, not all the dinosaurs were large.”

Peridot carefully strolls by a large cycad (a palm-like plant related to conifers) and rests herself on the ground, taking in the sight of the animals. You join her, a little more wary of the giants. “Dinosaurs were some of the most successful vertebrate animal groups that ever lived. They occupied nearly all of the major herbivorous and carnivorous niches on land and ranged all across the planet. What made them so great was the fact that they were able to carry their limbs directly underneath their bodies, as opposed to other types of reptiles that sprawled about on splayed limbs. Like… look at that lizard over there.”

Peridot points out a small, nobby-scaled lizard scuttling quietly nearby. “Notice how it runs. It’s only able to get a short distance before stopping to rest. That’s because of the way its skeleton is built. With splayed legs, a lizard has to move its body side-to-side, which only allows one lung to breath at a time. That way, it’s not able to get the oxygen it needs, and it has to keep resting to build back its strength. Now, pay attention to these dinosaurs. Notice how elegantly they move. That’s because their hips and shoulder girdles have adapted to hold the limbs directly underneath the body. With this arrangement, dinosaurs didn’t restrict their breathing by walking, and they could move faster and for longer distances as a result. Some dinosaurs even supplemented their lungs with a system of air sacs that allowed for constant oxygen consumption. Now that’s efficient!”

You both continue to watch the dinosaurs, who are beginning to move on after felling every tree they’ve eaten from. There is a young one amongst the adults. “Aww, cute. You might be familiar with these dinosaurs. They’re called _Brontosaurus_ . At 70 feet in length and weighing over 16 tons, these were powerhouses of muscle. Your Earth scientists haven’t really figured out just why the necks on dinosaurs like these evolved to be so long, but we have no doubt that it would have been a big help in feeding! Long-necked dinosaurs like _Brontosaurus_ had peg-shaped teeth for stripping the needles off conifer trees, and they needed to eat constantly just to support all their energy needs. Dinosaurs seem to have been endothermic, able to generate their own body heat, as opposed to most other reptiles which were ectothermic, where they need to sun themselves to get the head they need to function.”

Two _Brontosaurus_ face each other, each one eyeing the other closely. “Whuh oh… are we about to see some action? I imagine big dinosaurs like these could be really mean.” Peridot cranes her neck for a closer look. At the moment, one _Brontosaurus_ simple gives the other a smooch on the cheek. 

“Aww.” Peridot beams, “how sweet. Still, I was kinda hoping to see some action.”

Suddenly, the two of you hear a harsh clunking sound from behind. Peridot whips her head, wide-eyed and teeth-bearing. “Oh no. That sounds like the time machine!” She takes off after it, leaving you to trail behind. You push away cycad fronds from your path, huffing and puffing as you try to keep up with the gem. It isn’t long before you bump right into her, knocking her down to the ground with a “yeeugh!”

“Hey! Watch it!” Peridot grabs your shirt and yanks you down to her level. “And keep quiet! I’m trying to figure away out of this situation.” 

Cocking an eyebrow, you look in Peridot’s line of sight and see the problem. An intimidating carnivorous dinosaur has been playing with the outer shell of the time machine, using its mouth, hands, and feet to knock it around. Almost like an oversized house cat playing with a ball. It has three fingered hands tipped with very sharp, curved claws, and the top of the head is adorned with small bumps and crests over the eyes.

“That’s _Allosaurus_. It just so happens to be one of the largest of the Jurassic hunters around here, and it’s toying with my time machine like it’s some… some… some toy! Urrrrr! I could move it away with my special device… but I haven’t tested it on big things yet.”

After a while, the dinosaur starts pushing at the pod with its head. The limbs of the pod retract, giving the time machine its spherical shape. Soon it begins rolling along, as the _Allosaurus_ moves it away from you both.

“No no no no no! We have to follow it! Keep close!” Peridot quietly barks, slowly following the large predator.

…

It takes nearly half an hour before the _Allosaurus_ stops rolling the time machine about. In that time the landscape has changed from forests of conifers and groves of ferns to a rocky coastline, with rough waves crashing against the shore. There are all sorts of flying reptiles about in the strong gusts. For the moment, all seems well, and Peridot relaxes a little.

“Okay… okay, she stopped. I think we’re good. She’ll get bored and walk away.” Peridot says.

However, the dinosaur has other plans. After looking around the coast, the _Allosaurus_ eyes a particular rock and begins rolling the time machine towards it. Stopped just at the rock, the dinosaur gives a good quick with its hindlimb and send the pod striking against the rock.

“WHA?! STOP IT!!” Peridot yells as the dinosaur continues to kick the time machine at the rock. “IT’S NOT FOOD! STOP YOU’RE GONNA BREAK IT!” she starts crying. Pulling out her device, she rushes at the _Allosaurus_ , right before you can reach out and stop her. 

“YEEEEAHHHHHHH!!!” Peridot screams as she sends a laser from the device. It strikes the _Allosaurus_ , but only envelopes its hindlimbs and tail. Giving a huff and growl, the predatory dinosaur tries to turn and face Peridot, who begins an attempt to pull and drag it away from the time machine. The weight of the animal is a little too much for the device, which shuts off before long. Finally free, the dinosaur is now able to turn, and starts trotting towards Peridot. “Eep!” she yelps, before sprinting back towards you. “RUN! RUN!” 

Panicking, you grab some rocks and start chucking them at the _Allosaurus_ , which flinches from the small, annoying blows. It stops, sniffs towards you and Peridot (who is wrapped around your body in a frightened hug), and snorts. Taking leave, it trots back off into the forest.

You both sigh in relief, slinking down to the ground for a minute.

“That… was… close.” Peridot huffs, before looking down at her device. “I clearly have work to do on this thing.” She puts it back into her gem, before getting up and checking on the time machine. To her luck, there are only a few dings, but nothing too severe. “Remind me to stop somewhere soon to buff out these scratches.” You give a tired thumbs up to her.

Easing down, Peridot starts looking around along the beach, noticing all the small shells and things about. “You know… we’ve been hanging out on land for a while now. Let’s head in the time machine and see what’s been going on underwater! I could use a break from dinosaurs.”

After slowly getting up and entering the pod, Peridot steers the machine under the rough waves. Thankfully, the water is rather clear, so much so that the headlights aren’t needed. 

“As I mentioned earlier, life had rebounded dramatically following the Permian mass extinction event. But perhaps one of the greatest environmental changes for life on Earth occurred throughout the Mesozoic Era. At about this time, 150 million years ago, marine organics began a major shift in diversity. The main types of plankton found in the oceans prior to now were green algae, close relatives of land plants, but their numbers began to dwindle after the mass extinction as the chemistry and nutrient distribution of the oceans changed. At that point, another type of plankton, red algae, started predominating the base of the ocean food web. This kickstarted a chain reaction that cascaded throughout all of the major marine groups of organics. It was a marine revolution!”

Peridot takes you further towards the seabed, where you can make out many different types of ocean life. “New groups of corals developed, the direct ancestors of those that form coral reefs in the present day. There were new types of mollusks, including some of the first species of snails to use special organs to drill into the shells of their prey. And the first crabs and lobsters arrived on the scene, efficient predators that could crush hard shells with their pincers. The lobe-finned fishes declined noticeably, but the ray-finned fishes had begun to flourish into so many different types. It’s basically around this time that the modern ocean ecosystem developed.”

Taking the helm, Peridot begins her ascent towards the surface, but not before stopping to appreciate a pod of large dolphin-like reptiles. “Oh yeah, there were still some derivations from the present day, like these marine reptiles called ichthyosaurs. It’s funny, not just how quick it took land vertebrates to head back into the oceans, but how often it happened. These reptiles won’t be the last vertebrates to do so.”

As the pod rises, Peridot puts in some new coordinates. “The landscape needs just a little bit more time to reach its modern state, and to see that we have to go forward in time. Hang on!”

…

_120 Million Years Ago_

Just cresting over the top of a bright pink tree, the time machine lands on a steady row of branches. Pedals flutter all around the pod as you take in the sight of a much more colorful world. Pinks, reds, yellows, and purples dot the region, and there are familiar sounds of chirping and buzzing in the air.

“Ooh, I should really bring Pearl here sometime. Though I bet she won’t last long with all these dinosaurs all about.” Peridot chuckles, reaching into the chest and grabbing some snacks. She offers you a granola bar, and you take it happily.

“We’re in the next and final period of the Mesozoic, the Cretaceous. We’re still in the age of dinosaurs, no doubt about that. In fact, I think it’s safe to say that dinosaurs did even better during this period than the last! But I’d argue that the real stars of the Cretaceous Period were the flowers!”

Peridot opens the window just enough to pick a flower from the tree: it’s a magnolia. “Flowering plants were the last major lineage of land plants to evolve, and they are the most successful of them all. Palm trees, maple trees, grass, apples, orchids, cacti, venus flytraps… they’re all flowering plants! Starting as small, bushy aquatic plants, the ancestors of the flowering plants evolved a special arrangement of leaves called petals that often sported bright colors. Now, as you can see, this magnolia is a simple shade of pink, but if I flip an ultraviolet light on it…” which Peridot does “... you can see an even more elaborate display of color! Why is that?”

Pulling down the scroll bar on the holoscreen, Peridot causes the time machine to shrink yet again, but only to the size of a bee. Speaking of which… you notice some large forms buzzing around you as Peridot maneuvers around the giant flowers. 

“It seems the evolution of flowering plants is tied to the evolution of insects. During the Cretaceous, a number of different insect groups evolved that developed more along social lines. These insects created their own societies, where by a single queen gives birth to all the offspring, of which a few select forms may grow: soldiers, workers, and so forth. These insects worked so well together that they might as well be their own organism. They became eusocial! One line of insects, the cockroaches, gave rise to one such type of eusocial insect, termites, but those species became adapted to eating wood. What we’re concerned with is the other lineage, the wasps. Some of those eusocial species gave rise to the ants, while the other evolved into bees.”

Peridot follows one of the bees as it lands on a flower. The bee starts looking for nectar as pollen becomes brushed along its hairs. “Insects like bees really helped flowering plants get their start and take over the plant world. Flowering plants found that they could recruit insects to help with pollination by giving them sweet nectar to drink. They co-evolved together: it’s a whole different type of fusion! Some of these relationships became so intense that some insects can only ever feed on the nectar of one type of flower, and some flowers can only be pollinated by just one kind of insect. That certainly makes them special, even though they become more vulnerable to environmental risks.”

The bee suddenly stops for a brief moment before flying away rapidly. This causes all the other bees to start buzzing off, but not before one unfortunate bee gets trapped between a pair of giant, toothy jaws. Peridot yelps and pulls the time machine away, setting the scroll bar up to make the pod just big enough to remove you both from the threat. The deadly maw turned out to be the beak of an odd bird, which perched on the tree next to the small time machine.

Peridot coos, “aww, it was just a little birdy. Towards the end of the Jurassic, one lineage of dinosaurs lengthened their arms and changed their outer coat of fluff into branched feathers. The muscles in the breast became strengthened and allowed for rapid motion of their wings. These dinosaurs, originally using their feathers for insulation, started using their wings for balance while hunting prey animals as well as providing lift when running along tree branches. Eventually, powered flight evolved, and the skies became filled with birds!” 

The time machine, grown back to full size, flies out across the colorful Cretaceous landscape. You take in the great herds of long-necked dinosaurs, small collections of horned dinosaurs, and a small pack of tyrannosaurs on the prowl. A pair of flying reptiles, pterosaurs, soars above the pod. It’s a world of reptiles indeed.

“As much as I’d love to stay and see more dinosaurs, we really should continue on with my story. And that means that we have to come to another sad part of the story.” Peridot, with a bummed expression, takes the time machine higher upwards until the entire planet is visible. There is a familiar shape to the continents now: Pangaea has since broken up and most of the familiar land masses are nearing their present-day locations. Africa and South America are now separated by a very thin, newborn Atlantic Ocean; Australia is starting to break away from Antarctica; and North America and Eurasia are just barely touching towards the poles.

“The dinosaurs were the dominant land animals for the remainder of the Mesozoic Era, but like all great animal dynasties, their rule came to an abrupt end. Allow me to demonstrate.” Peridot sets time in a fast-forward motion yet again, and all appears normal at first. The continents slowly move, but you notice that the sea levels have begun lowering and that puffs of volcanic smoke are radiating from India, which has begun separating from Madagascar. Peridot stops quickly and the clock reads: _66 Million Years Ago_. 

“A drop in sea levels and a rise in intense volcanism had started causing problems for life on Earth, though for a little bit it seemed that things would recover just enough so that the usual pace of things would remain the same. And then came some bad news, crashing down. Literally!”

Peridot turns the time machine in such a way as to give you a good view of the Gulf of Mexico. “Don’t blink” is all Peridot says as you watch a tiny blip slam into the Earth and send an enormous cloud of debris into space. The light is so intense that you can’t help but look away for a few seconds. When you turn back, the bright explosion has turned into a ring of death that begins encircling the entire planet. 

“The end of the Cretaceous, and the Mesozoic, coincides with another great mass extinction event. A rock from space - we don’t know if it was an asteroid, a comet, or a meteor - slammed into the planet with the force of 100 trillion tons of TNT. After impact, earthquakes and hundred-foot tsunamis engulfed much of the land, as you can see right now. It was total devastation. It won’t be too long before the impact winter kicks in, when clouds from the explosion blanket the Earth in a darkened, snowy apocalypse that shuts down all major ecosystems. 75% of all organic life died out.”

Peridot holds up the little magnolia flower, still safe in the time machine. “Thankfully, the casualties are not as severe as those in the Permian. No major groups of life died out this time, many organics survived relatively unharmed. Even the dinosaurs lived through it… remember, birds are dinosaurs! And if it wasn’t for this mass extinction event, the world as you know it wouldn’t be here! For all we know, humans probably wouldn’t have evolved. I wonder if Pink Diamond would have liked a planet of dinosaurs?” Peridot puts a finger to her chin in contemplation. “Anyway… I shouldn’t be too sad. If humans hadn’t evolved I wouldn’t have gotten to meet Steven or Connie or Greg… or you.” You give Peridot a smile and a pat on the back.

“Come on… let’s proceed.” She blushes.

…

**_To Be Continued!_ **

**Notes for the Chapter:**

> Special thanks to Firefly's Multi-Authored "Evolution: The Whole Story" (2015), Darren Naish & Paul Barrett's "Dinosaurs: How They Lived and Evolved" (2016), and Dr. Thomas Holtz's UMD GEOL 102 "Historical Geology" Online Lecture Notes for information.


	5. It's Only Human

**Summary for the Chapter:**

> From the Age of Mammals to Homo erectus

_50 Million Years Ago_

With the sight of the immense bolide impact fresh on your mind, Peridot takes the time machine into the heart of a vast tropical forest. Huge cypress trees were interspersed with an abundance of different flowering trees, shrubs, and climbers. You even make out what appear to be citrus or mango like fruits growing on some of the broadleaved trees, alongside palm trees. The tell-tale sound of birdsong and insect calls is ever present.

“Following the extinction event at the end of the Mesozoic Era was the Cenozoic Era, which is the time of Earth’s history that you were born into. In fact, all of human history as well as the last 66 million years of life on Earth are all encompassed by the Cenozoic!” Peridot explains, opening the pod and jumping out. “We’re standing in a world that has completely recovered from the devastation: a lush paradise where tropical forests are growing all across the planet, even at the poles!” 

You follow beside Peridot as you take in the views. A group of heron-like birds is residing in a pool, as flocks of parrots fly from tree to tree. “There are still plenty of dinosaurs around, in the form of birds, and most of the major groups we have in the present day had evolved around this time. However, this is a world dominated by mammals, like you!” Peridot grins, “mammals actually evolved early in the Mesozoic, but we didn’t have time to find any. 50 million years ago, the three major groups of mammals were all well-established: the egg-laying monotremes (like the platypus and echidnas), the marsupials (who carry their young in pouches, like kangaroos and opossums), and the placentals (which includes all the rest). In the end it was the placental mammals who would rise among their kin, eventually taking over most of the major herbivore and carnivore niches on Earth, save for some places.”

Before you can keep walking, Peridot grabs your arm and stops you. Something has caught her attention by the edge of a river. She turns, placing a finger to her lips, and takes you closer. Residing in between two young redwood trees, she points towards the shoreline. “Take a look at that!”

You spot what appears to be a strange group of mammals playing in the water. They’re very dog-like in their face and body, but that’s where familiarity ends. They have hoofed feet and a very slinky, otter-like tail. “Can you guess what mammals will descend from these guys?” Peridot asks, poking your arm playfully. You remain dumbfounded, giving her a comedic shrug.

“These are called _Pakicetus_ , and they are some of the oldest known whales!” Peridot says, to which you turn to her and cock an eyebrow. “Seriously! Here, pay attention to the placement of their eyes. They’re high up on their skulls! That helps them see above the surface while they forage in the river for food. And you won’t be able to tell, but they have a special mutation in their ear bones that allows them to make out sounds underwater. Overtime, mammals like _Pakicetus_ will become more streamlined, losing their fur while they increase the length and strength of their tails for swimming. They’ll turn their hoofed feet into fins, and their eyes will move to the sides of their heads while their nostrils move up to their skulls. Next thing you know, their hindlimb bones have sunk into their bodies and they have flukes at the ends of their tails. In just 10 million years, these animals will grow to lengths of 60 feet or more, becoming fully-fledged marine mammals. It’s a whale of a tale, if I do say so myself!” Peridot chuckles, as you roll your eyes and flick her nose.

“Hey!” she yells, causing the _Pakicetus_ group to sense your presence and bolt under the water. 

“Aww man, you scared them off!” she groans, before hearing the stamping of feet behind a grove of shrubs. “Oh well, there are plenty of other mammals to see. Let’s look over there!” 

Peering over the dense foliage, you both witness a collection of smaller mammals running in unison. They too are dog-like, but in size rather than appearance. A tiny whinny gives their identity away clearly. “These are early horses, called _Eohippus_. They have four tiny hoofed-toes on their forefeet and three toes on their hindfeet, perfect for scampering through the undergrowth of forests! And they need to be able to run, because there are always predators around!”

As if on cue, one horse straggles behind as the massive form of a crocodilian appears behind it, grabbing the poor thing by the ankles and trashing it about. Now dead, the predator quickly swallows the horse whole, and proceeds to gallop away on lengthy, hoofed legs.

“Yeesh, I do not want to run into a planocraniid crocodile in a dark alley. I’d rather take my chances with an angry Yellow Diamond… and I have. Nuehehe.” Peridot comments, crossing her arms.

You make out a noise overhead, motioning to Peridot. She looks up with you to find a small congregation of bats fluttering on the branches of a tree. They don’t look particularly unique compared to the bats you’ve seen at home. “Oh cool, bats!” she turns to you, “you don’t seem impressed? That’s fair. We don’t actually have a good idea what the first bats looked like, because the earliest fossils we have already show animals with full wings and even rudimentary echolocation, like these ones. Still, they are pretty impressive, bats are the last vertebrate group to take to the air.” 

The two of you continue to move through the forest, making your way back to the time machine. You pass by all sorts of early mammals, all the representatives of living groups are there. As you enter the clearing where the time machine is parked, you are stopped in your tracks as you witness a confrontation between two tree-living mammals right above the pod. Peridot takes notice and gives a small smile as she wraps an arm around your shoulder. “Check it out! Primates!”

Taking a seat on a nearby rock, Peridot observes the fighting animals carefully. “Well this is awfully convenient. The species that are having this little argument each belong to one of the major groups of primates!” She points to the ones at the left, which have lanky bodies, fluffy tails, pointed ears, and faces tipped with a dog-like snout. “Those are _Notharctus_ , members of the wet-nosed primates. They used to be very common around the world, but have been supplanted by mammals like those over there.” Now, she points to those on the left, which are much smaller, with rounded faces, wide ears, and thinner tails. “Those are called _Eosimias_ , and they belong to the dry-nosed primate group. The descendants of primates like _Notharctus_ will give rise to the lemurs, lorises, and bushbabies, while those of mammals like _Eosimias_ will spawn tarsiers, monkeys, and apes.”

The two groups continue to chatter as one of the _Eosimias_ takes a swipe at a _Notharctus_ , who proceeds to run off, while the others are chased likewise by the rest. 

“What makes primates unique among mammals are traits like stereoscopic eyes, which give them 3D vision, that way they can have depth perception while running through the trees or finding food.” Peridot flicks her thumb in and out a few times, “opposable thumbs are pretty good too, it turns out. They’re much easier to use to grip branches or catch delicious fruits and bugs than paws. And having a larger brain-to-body ratio helps process all of this! Primates are smart!” 

Checking if the coast is clear, she leads you back to the time machine, closing the window before anything climbs inside. “For the next few million years after this time, the Earth will experience a slow yet dramatic period of cooling, caused by mountain-building and the change of continents. Antarctica, for example, will finally end up an island continent, as Australia and South America break away from it. This will allow a new ocean current to form around the landmass, severing the warm currents in favor of cool ones. The landscape will get colder and drier. Glaciers will start to form. The great rainforests will retreat, being slowly replaced by temperate deciduous forests, where the trees actually shed their leaves with the seasons. Mammals and other organics will evolve and die out, and the world will begin to get much more… familiar.”

…

_Western North America, 20 Million Years Ago_

Now the time machine appears in a yellow-orange grassy field that extends for hundreds of miles outward. There are a few scattered trees here and there, but the dense jungle is all but gone. Peridot calmy opens the window and a gentle breeze flows into the pod, filling your lungs with an earthy scent. 

You’re the first to get out this time, and you plant your feet onto soft soil, the reeds breaking beneath you. Peridot comes out, her eyes all starry. 

“Ooh. Feels like home,” she says. “Come on, let’s stand on that hill over there, I want to get a better view!”

You follow as she tredges up the slightly steep hill, finally making it to the top. When you arrive, you give a small gasp as you witness a massive herd of horses running through the plains. They’re accompanied by small camels, strange antelope-like creatures, and many others. Feels like a safari.

Stretching, Peridot falls back-first into the grass, catching you off guard. Laughing, you lay down beside her.

“Wow, this is so great. While much of the world turned into deciduous forest, many parts were dramatically affected by the cooling and drying of the climate. Grasses, a type of flowering plant that had originally evolved in the Cretaceous, was hardy enough to overcome the change, and eventually spread out over many parts of the world. It was around this time, 20 million years ago, that the first grasslands developed. Prairies, savannas, steppes, meadows, all based around a single type of plant. And with their spread came a sharp change in animal and plant life.”

A small field mouse grasps to a large reed, looking down at your resting forms. It flickers is nose, only the jump back quickly as a small snake slithers past. The reptile keeps its distance from you. 

Peridot continues, picking up a dandelion, “some types of flowering plants became remarkably hardy, able to live amongst the grasses, which were often prone to repeated wildfires. These species, called composites, were able to take root and grow so fast that they often outcompeted many other wildflowers that grew nearby. Flowers like daisies, dandelions, and sunflowers belong to the composite group. Smaller animals also took advantage of the grasslands, with rodents, rabbits, and shrews growing in number and living in burrows, as reptiles like the first venomous snakes followed them.”

You hear a growing tapping sound, which makes the two of you nervous. Staying low amongst the grass, you both hold onto each other as a single horse head pokes through the reeds. Peridot sighs in relief as the horse snorts and starts walking away. Finally standing up, you both follow after it at a safe distance.

“That horse is a long way off from _Eohippus_! As the forests retreated over time, many groups of hoofed mammals that were used to browsing on leaves took to living in grasslands, and they adapted their bodies accordingly. Horses, camels, and other herbivores lengthened the roots of their teeth and mutations allowed them to constantly grow in life, since eating grass wears down teeth! Their legs lengthened too, and most of them lost most of their toes. Horses, for example, have reduced all their digits to just one single hoof, which corresponds to your middle finger.”

The horse continues to graze, before a noise stops it in its tracks. Giving a yelp, the horse bolts off, with the whole herd following in turn. A pack of enormous dogs is giving chase behind, trying to fragment the herd to pick off a younger foal.

“Wow! _Epicyon!_ Those are some of the biggest dogs that will ever exist!” Peridot jumps in place, “like I said, there are always predators around! Carnivorous mammals followed the herbivores onto the plains, developing their own traits to suit this new world. They too lengthened their legs, and started running on their toes rather than the soles of their feet. To protect themselves, herbivores started forming larger herds, and many predators took up pack hunting for the first time. It was a big evolutionary game of running and gunning!”

You both continue to watch. It’s a fantastic chase, but the horses manage to get away. The great dogs are too tired to continue, and they sulk away to rest for a later chase. You both head back to the time machine, and Peridot sets new coordinates.

“Grasslands will continue to be a major ecosystem on Earth, and ever more animals and plants will adapt to its riches, but many more will still stay to the forests, developing their own unique lifestyles. For the primates, they’ll continue to diversify. Monkeys, for example, will switch to a mostly herbivorous diet of leaves and fruits. They’ll be able to see in full-color vision, which helps when you want to know, say, what fruits are ripe. Some of these monkeys will grow in size, not just their bodies but their brains too. Their shoulder joints will become more mobile, so that they can swing their arms freely through the trees. And they’ll begin to reduce their tails till there’s none left at all. Their descendants will become apes, and that’s just who we’re about to see next!”

…

_Present Day Ethiopia, 4.4 Million Years Ago_

The time machine stops right under the grove of a gangly tree. Its leaves are very thin and prickly, and ants are crawling all about it. Peridot opens the window and begins flicking ants away as they start entering the pod. “Okay, get out for a second.” she nudges you out of the machine, sending you rocking forward awkwardly. You turn to see Peridot grabbing a branch and swinging at the swarming ants, but her luck runs short as ants start falling from the branch itself! Screaming, she throws the branch and pulls her little grabbing-device from her gem. Pointing it at the time machine, she shoots the laser and picks up the entire pod, giving it a good shake. Finally, she readjusts the pod and moves it to a clearer location, away from annoying bugs.

Huffing, she turns off the laser and puts the device back in her gem. She turns to you, her hair slightly ruffled, “we definitely don’t want any stowaways on this adventure.” 

You giggle as Peridot fixes her hair, before giving a wide-armed gesture. “Welcome to Africa! The birthplace of humanity! Just two million years prior, apes ranged all across Africa and Eurasia. There was a brief warming period where many of the forests expanded, and apes took advantage of all the available space, but by 6 million years ago, the cooling commenced again and the forests began to shrink. Many species of apes died out, their niches left vacant for different types of monkeys to fill. There was one type, however, that managed to survive and flourish in the drying ecosystem. So, here we are 4.4 million years ago to see a descendant of this ape! Let’s go!”

As you follow Peridot, you take notice of the environment. It’s an open woodland: there are trees all around, but there are noticeable gaps between them, filled by grasses, ferns, and other low-growing plants. You can make out the vast savanna beyond the trees, where vast herds of long-extinct animals graze and hunt. Peridot turns to you, walking backwards, as she makes a “camera” pose with her hands.

“Just take a second and think about how you’re moving: balanced on two legs. The group of apes that humans belong two are known as hominins, and they’re special because they were bipeds. They moved on just two legs, and by having to do so frequently, their skeletons became modified.” Peridot pulls out her tablet from her gem, displaying a photo of a human skull. “Notice that hole at the base of the skull? That’s called the foramen magnum: it’s where your spine attaches to your head! Apes and other mammals have this too, but it’s positioned at an angle. Hominins, on the other hand, have theirs facing vertically, to keep their heads up over their shoulders. It’s definitely easier to look around that way.” She changes the picture again, this time to a photo of a pelvis. “Then there’s the pelvis, which had to become bowl-shaped to better support the organs, not to mention it helps keep the hindlimbs underneath the body.” Lastly, she changes the image to a photo of the bones of the foot. “And here’s the foot, now with a firm heel to keep you up on your feet with a spring in your step!” 

Peridot puts the tablet away. “The earliest hominins evolved between 12 and 7 million years ago, having split from a common ancestor with chimpanzees. That is to say, chimpanzees and hominins shared the same ancestor, making them very closely related. One of those earliest species, called _Ardipithecus ramidus_ , is who we’re here to see.”

The two of you reach the corner of a grove of trees, entering into a much denser patch. Peridot takes a quick peek around the corner, before motioning you closer. As you look, you see a family of five _Ardipithecus_ all feasting together. One has collected some soft nuts and is gently popping them into his mouth, one at a time. Another, a mother with an infant, is sipping from a cracked bird’s egg, the baby looking curiously at it. The other two are digging for grubs.

“Aww, a little family.” Peridot coos, “ _Ardipithecus_ lived in a mosaic environment, meaning that their home sported all sorts of different regions, from the open woodland we just passed, to the grassland periphery, to the more dense patches of forest, like over here. That means that these hominins have access to a wide variety of resources, and most foods are available to them. But there are always dangers: nothing scarier than a saber-toothed cat or a giant hyena to keep you on guard.”

One of the _Ardipithecus_ stops digging for grubs and perks her head up. The others look on with tense curiosity. Sniffing the air, the hominin gives a small hoot, and before long the entire group is quickly moving towards the trees. 

“That’s why it helps to be able to move bipedally, you can get from one patch of trees to another and save energy doing so! A human like yourself actually uses 75% less energy walking on two legs than a chimpanzee does on all fours. However, that doesn’t mean that tree-living is no longer a viable lifestyle!”

The _Ardipithecus_ family ambles up into the trees, using their hands and feet to grip onto the trunks of the trees. Once among the branches, they calm down, one of them still giving a look out in case.

“The hands of _Ardipithecus_ are rather simple in their build. They don’t knuckle walk like chimpanzees, but use their palms for walking. Their feet are very traditionally-ape too: with a big divergent toe for extra grip, yet they already have the firm heel for additional support on two legs. It’s an effective combo, and they can even stand and move upright in the trees. Check it out!”

Peridot points at one of the hominins, the mother with the infant, who is currently walking upright along a large branch. She settles down at the end of the branch on a nice pile of leaves.

“Sweet.” Peridot comments, before leading you back to the time machine yet again.

…

_Present Day Ethiopia, 3.2 Million Years Ago_

Piloting the time machine, Peridot flies you over expansive African savanna. You move past herds of elephants and buffalo, and there are pairs of giraffes on the move. She lowers the pod down just enough to cruise comfortably past a small, winding stream.

“I’ve only jumped us forward 1.2 million years. We’re still in the same region we were last time, but now the grasslands have expanded even more. Those mosaic environments are much further away now, and any hominins that stayed put had evolved to better suit their new grassy plains. They were now obligate bipeds: fully committed to a life on two legs. The long big toe has now aligned with all the other toes to form a more recognizable padded foot. After hominins like _Ardipithecus_ , many different species evolved and often co-existed together.”

Peridot lands the time machine at the edge of a large basalt quarry, interspersed between some thick patches of grass. “With luck this group hasn’t seen us yet.” she comments, before leaving the pod with you. Taking careful steps, you peer out over the grass to see a slightly larger group of hominins collecting and working with stones around the quarry. They’re much larger than the _Ardipithecus_ you saw earlier: two big males about 5 feet tall, and four females only 3 feet tall. One of the males is quite scruffy in their face, with a beard sporting patches of white, as are one of the females.

“These are called _Praeanthropus afarensis_. What’s remarkable about hominins like these is that they will be some of the earliest known members of your family tree to figure out the process of making stone tools! Like other apes, they understand how to manipulate things like sticks and leaves and turn them into quick tools, but the process of shaping a rock takes much more effort and skill. They had to visualize what they wanted from a blank stone, and then work hard to get their desired results.” Peridot explains.

You watch one of the _Praeanthropus_ select a sizable stone (about the size of a football) and place it on the ground. Taking another slightly smaller stone they had saved nearby, the hominin begins striking the small stone against the big one, producing some flakes that bounced away. It proceeds to repeat this motion all around the rock, making slow progress.

“Yeesh, I forgot how long this could take. If you don’t mind…” Peridot begins, as you give a small thumbs up. “... that’s what I thought.” She takes you back into the time machine and fast forwards only for 30 minutes. Once you both exit, you see that the group has now finished several stone tools. They begin picking them up and leaving the quarry.

“Later types of stone tools would take many hours to construct, as their designs became more specific and tailored to different species. Let’s follow this family and see what all this work was for.” Peridot suggests, before activating the time machine’s limbs and walking at short distance behind the group.

It’s only a 15 minute hike and one of the female _Praeanthropus_ stops, looking around and giving a motion with her hand. Everyone else observes as she gets on her knees and pats the rough dirt. Before long she’s hitting the soil with her stone tool, sending puffs of pebbles and dirt flying outwards. The other _Praeanthropus_ follow her lead. 

Peridot nods her head, “ohhh, that makes sense. That dirt is too hard for sticks: they created these tools to be able to actually dig! I can already guess what’s on the menu.”

One of the other females has hit her mark. Frantically hooting, she paws away the rest of the soil and pulls out a very large tuber. Everyone cheers, panting and hooting as they continue digging for more. The successful female grins and places the root vegetable beside her. Then she’s back to digging.

“Hominins like _Praeanthropus_ had big canine teeth that were great for stripping tough, fibrous plants. These tubers - or underground storage organs - had all of the essential nutrients they need to make it through these hot, dry times in Africa. They even provide fresh, clean water! Which is helpful if you don’t want to try your luck at the edge of a lakebed… crocodiles and angry hippos are a threat here.” 

As the group celebrates the uncovering of more tubers, Peridot sets new coordinates in the time machine. “For the most part, hominins were herbivores, only occasionally supplementing their diet with small animals. But that was soon to change!”

…

_Present Day Tanzania, 2 Million Years Ago_

The landscape has changed slightly: it’s still a savanna, but now Peridot has taken you to the edge of a vast lake, surrounded by an abundance of acacias, palms, and other trees. It’s an oasis! As the time machine descends, Peridot nudges your shoulder and points below, where you spot a pride of lions that has just made a kill. They’ve completely surrounded a deceased kudu (a spiral-horned antelope) and the male has started eating at the neck. Vultures and storks are scattered several feet away waiting for their chance and a lone jackal is cautiously sitting further still.

“Yeesh, thank goodness Lion only eats lizards. Steven’s eyes must remain pure!” Peridot comically states, “anyway, we’re not here for the lions. What we want to see are the band of hominins much further away. It’s lunchtime and they’re not taking any chances!”

The time machine rests between the two congregations, just out of notice. To play it safe, you both stay in the pod. 

The hominins look much more familiar now. Their faces are noticeably flatter, lacking the jutting jaws of the earlier _Praeanthropus_ , but they’re now sporting significantly large brow ridges over their eyes. They’re still hairy, but their body covering has reduced quite a bit. Most notable of all, all the males and females share the same height.

“Your Earth scientists have designated these hominins, _Homo habilis_ , as the very first humans. All organics on Earth have scientific names, a genus and a species, that is understandable to people all around the planet. When the first members of the genus _Homo_ evolved, around 2.8 million years ago, they had developed into such distinct hominins that they looked very different from the earlier species, like _Praeanthropus_. What’s more important, however, is that early humans behaved differently too. They started cooperating on more and more tasks. Different adults started sharing in the care of infants, allowing the mothers a chance to rest once and awhile. And humans started expanding their diets to include flesh from other, larger animals, but to get food like that you had to be bolder.”

Many of the group of _Homo habilis_ were wielding some sticks and branches, while two others were tightly holding onto a collection of stone tools. As they approached the lion pride, some of the humans started calling and waving the wood in the air. One smaller member even starting picking up stones and chucking them at the big cats. One lioness runs off, while two others started snarling and closely guarding their kill. The humans only shouted louder, and one threw his stick right at the big male. It wasn’t long before all of the other lionesses ran off a good distance, the male lagging behind. As soon as they could, the _Homo habilis_ ran up to the carcass and started dividing themselves to different sections.

“I think we can get a little bit closer for now. They’ll be so preoccupied with this that they won’t notice us much.” Peridot says, taking the pod a little ways towards the carcass. They’re about 15 feet away, and a vulture has perched on top of the pod.

“What we just witnessed was called power scavenging. Why hunt after big game when you can just let the predators do it for you?” Peridot explains, “Originally, this practice would have started out with the humans coming across already eaten remains. Only later would humans start intimidating the predators into getting fresher meals, which is what these humans have done. Their primary goal now is to get as much food as they can before the lions come back.”

The _Homo habilis_ have managed to slice through the thinner skins around the limbs and neck and have begun to split open the bones with their stone tools.

“These stone tools - they’re called Oldowan - are much more complex than the earlier ones that _Praeanthropus_ used. These stones can do more than just dig, they’re a combination of knife, hammer, and pick-ax: like a prehistoric swiss-army kit!”

One human has managed to split a bone in two. Using his finger, he scoops along the inside and pulls out a wad of marrow. He puts it in his mouth and smiles, before hacking at the sides of the bone to pull it away from the leg. Some others follow suit, separating the bones they need. Three individuals have started separating the fat from the muscle. “Notice how they’re not getting at the meat.” Peridot points out, “The fat and bone marrow from carcasses like these give a lot more calories than regular old red meat, which is good because nutrients are hard to come by around here. And this is critical in the development of the human brain. Your brain, right now, is 60% fat. Early humans like these would have needed a lot of it just to support themselves, since members of the genus _Homo_ had larger brains than their ancestors.”

It isn’t too long before the pride of lions started trotting back towards the carcass. One _Homo habilis_ gives an alarm call as the rest of the family picks up their stone tools, bones, and pieces of fat and bolts away as fast as they could. Peridot takes the time machine and flies off into the air, just as the lions return to continue their feast.

“Teamwork, ingenuity, and a little courage: these are the traits that define humans, and your ancestors were certainly all of that!” Peridot nudges your shoulder, “Eventually, humans would simply add to their knowledge base, and lead the way for some of the most creative ideas ever thought!” Happily punching a new time period, Peridot sends the time machine in a flurry in lights and sparkles.

…

_Present Day Java, Indonesia, 700,000 Years Ago_

It’s dusk when the time machine appears above the canopy of a great tropical forest. The woodlands are open, with many clearings covered in dense grasses, shrubs, and ferns. There are small watering holes here and there, and you can make out great mountains in the distance. Peridot flies on, confidently. “Around the time that we visited _Homo habilis_ , early humans had already began to expand their range outside of the African continent, having already made it as far as East Asia. This happened over many tens of thousands of years, as regional climates changed or as resources shifted. The humans we’re about to meet, _Homo erectus_ , have made Eurasia their home continent, and we’re at the southernmost part of their range.”

The time machine flies down into the woods, passing a few tall trees before settling softly between two bushes covered in beautiful, red flowers. Peridot leads you out of the time machine, and you plop your feet into the thick undergrowth. Several butterflies flutter away as you trudge along, and you find yourself wiping your sweaty brow. 

“Yeah,” Peridot notices, “it’s quite humid here. Earlier, back in Africa, humans were having a difficult time moving through the hot, dry savannas. Being bipedal helped a little bit, since there wasn’t as much surface area exposed to the sun as before, but their furry bodies made overheating a common problem. So, around 1.2 million years ago, a series of mutations arose that reduced the density and thickness of the hair on the body, made the skin darker in pigment, and spread sweat glands all across the body. This was an ideal arrangement, because now humans could better regulate their body temperature by sweating, while their dark skin prevented much of the sun’s ultraviolet radiation from hitting them. As they spread across Eurasia, they took these traits with them.”

You push away more branches and leaves as you follow Peridot. All of a sudden, you hear movement in the distance. It sounds like something running, with the footsteps sounding frantic and panicked. As the sound increases in volume, you pull Peridot back in time as a deer sprints across your path.

“Nyeah!” Peridot yelps, clinging to your arm. “That was really close! Thanks for the save.” 

You nod, before looking back at the deer, which has moved into the brush. And yet, you hear more sound. It feels like multiple animals running in unison. Not taking any chances, you lead Peridot behind a tree trunk, and watch as several humans enter the clearing. They’re very tall and very nude, wielding sharpened, wooden spears, and moving on thin but muscular legs. They stop for a quick rest. One individual, a male, is pacing around the area as his companions stand there, breathing heavily. He has his hand out as he walks, as if reaching forwards. To your (and Peridot’s) surprise, he finds you both behind the tree.

“Umm…” Peridot gulps. 

The man stops, peering at you both with curious eyes, and speaks something unintelligible to you.

You think fast. You point your finger in the direction of the deer. 

Smiling, he calls back to his friends, and in no time they’re running towards the deer’s path. With an almost kind expression, he urges you both to follow him.

“Sure, the pleasure’s all ours!” Peridot talks back, with an unsure tinge to her voice.

Soon, Peridot and you are running alongside a group of _Homo erectus_ , hunting a deer. You didn’t prepare for this type of exercise, and before long you’re huffing and puffing as you keep up.

“Well, I didn’t expect to actually participate in the events of my story… but I guess I should be prepared for anything!” Peridot laughs, turning to you as you run. “These humans are engaging in endurance running. That deer knows it’s vulnerable as prey, so it’s giving it all it’s got! By doing so, however, it’s wasting a lot of energy and stamina. For a hunter _Homo erectus_ , persistence is key. This deer is much faster than these humans, and they know that, so why waste energy trying to catch up to it? By chasing it as this reasonable pace, these humans can keep up while the deer slowly exhausts itself. This process can sometimes take days, so who knows how long these guys have been at it?!” 

The chase goes on for several minutes, and you readily notice that the time machine is now long behind you. One of the hunters (the one who found you both) stops and gives a signal with his hand. You’re all now focused on him. He slowly moves past some bushes and sees that the deer has collapsed on the ground, resting on its front limbs. Panting deeply, it notices the hunters, but doesn’t do anything to move. Cautiously, the hunters approach. You stay behind with Peridot, who’s all eyes on the deer. “Yep. It’s over.”

With a swift thrust, the _Homo erectus_ male delivers a jab into the deer’s neck. The others follow likewise, stabbing the animal in the hide. Within a minute, the deer is dead, and the men give out a victorious yell. Such hard work has finally led to success.

One male looks over and finds a bush filled with berries. He walks over, takes a close look, and begins picking at them. Some of the other males take a seat and stretch their bodies, while the hunter who delivered the first blow walks up to Peridot and you. He speaks to you, specifically, and smiles as he gestures with his hands. You can’t make out what he’s saying at all, causing Peridot to poke at your side. “I think he’s thanking you. Just smile and nod your head.” As you do so, he nods back, before one of the other males returns with a handful of berries. He offers them to the hunter, and then to you both.

“Oh? Wow, thanks!” Peridot says, taking some berries. You pick a few as well, and they’re very refreshing after such a long run.

…

Peridot decides that it would be a good idea to follow the band of hunters home, which turned into an hour long hike. You’re just grateful that you’re not one of the two hunters dragging the heavy deer by the hindlimbs. One male is carefully eyeing around the forest, as if keeping watch for predators. 

It’s nearly nightfall when you all return. The campsite for these _Homo erectus_ looks surprisingly comfortable. It’s located at the base of a steep, tree-covered hill, and there is a series of branches and sticks that have been placed all in a row around the camp, acting as a sort of short-fence. There’s a fire going on at the center, in a dug-out pit. Several happy faces greet you all as you enter, including several children. They stop when they catch site of Peridot and you, but welcome you all the same after the hunter explains your help. 

“It looks like we’re visitors for the night. I hope you don’t mind a sleepover?” Peridot sheepishly says, to which you shrug your shoulders. It could be worse.

As you both sit by the fire, Peridot eyes it with passion. “Hominins have probably been relying on fire since the first species evolved. Even chimpanzees like to follow forest fires, picking up the charred animals and plants in their wake. We have evidence that humans like _Homo erectus_ were creating campfires by 1.6 million years ago, though don’t ask me how they set up this one. They could very well have collected it from a brush fire for all I know.”

You turn to find some of the women and men butchering the deer carcass. They’re setting aside the marrow and fat, but they’re also selecting cuts of meat and placing them on small flattened pieces of bark, which are gradually being placed at the edge of the fire, cooked, and passed around. 

“ _Homo erectus_ and its relatives were probably some of the first humans to actually cook their food. Whether it’s meat or vegetables, cooking helps breakdown food for easier consumption, making it nice and soft and killing any harmful bacteria that might be living in it.” Peridot explains, as one of the women hand you both plates of meat. Simultaneously, you give each other an unsure look, before Peridot chuckles. “At least it’s cooked.” She picks up the meat, but it’s still a bit hot, causing her to flap her hand to blow away the head. “Ah!” 

You hear a giggle from across the campfire. One of the _Homo erectus_ women is laughing at Peridot’s accident. She’s sitting down with her legs out, as she presses her hand to her enlarged belly. She’s pregnant.

Waiting a little bit longer for the meat to cool, you take a bite. It’s pretty much like the venison you’ve eaten before, though it’s pretty bland. Guess you’ll have to wait a couple tens of thousand years before spices are discovered.

As Peridot eats, she turns to see two young _Homo erectus_ playing around with sticks. There’s an elderly woman sitting close by, holding one of the wooden spears in her left hand and a stone tool in her right. She’s talking to the kids, making sweeping gestures with her right hand across the end of the spear. One child takes his stick, picks up a rock, and attempts to copy the elder.

“Ahh, collective learning.” Peridot sighs, “that’s a hallmark of humanity. Your ancestors had the ability to build up their knowledge of the world, just like other animals. Unlike them, however, that knowledge didn’t vanish when the animal died. They were able to teach what they knew to other members of their kin, including their children, thereby passing down that information from generation to generation. Not only that, but those descendants could build upon what they learned, leading to ever more innovations and inventions!”

You smile at the young _Homo erectus_ , who are acting very cute as they copy their teacher. Suddenly, a cry echoes across the campsite, and you bring your attention to the source. It’s the pregnant one! She’s crouched over her stomach, caressing it. One of the males rushes over to her, rubbing her back and talking to her face to face. Everyone stops what they’re doing and rushes over to her, including Peridot and you.

“Oh my stars, she’s having a baby!” Peridot panics, dropping her plate. “Let’s give her some space, come on.” She leads to towards the end of the camp, where the elderly _Homo erectus_ has brought the children. Before long, the pregnant mother is laying on her back, breathing in and out, as another female caresses her face and arms, speaking to her.

“Bipedal locomotion originated at the beginning of hominin evolution, only followed much later by the expansion of the brain. By the time humans like _Homo erectus_ evolved, the process of childbirth became significantly dangerous because the head was almost too big to pass through the opening of the pelvis. Childbirth became much more painful! Thus, as you can see, the practice of midwifing took hold. Social bonds among _Homo erectus_ were already strong enough, and thankfully this mother has someone to keep her safe while she has her baby. If she was alone, she could very well die.” Peridot observes, as the mother continues to cry out in labor. 

This goes on for a couple hours, and with one final push, her baby has arrived!

While giving her some necessary space, the group crowds around the mother. She’s taking deep, exhausted breaths as she holds her wailing infant, who instantly clings to her chest. One of the males, seemingly the father, sits beside her. The two nuzzle their faces, before turning to look as their new baby.

“Aww.” Peridot coos. You can’t help but smile too. It’s way past midnight, but sleep is the last thing on your mind as you watch this happy family.

…

**_To Be Continued!_ **

**Notes for the Chapter:**

> Special thanks to Firefly's Multi-Authored "Evolution: The Whole Story" (2015), Donald Prothero's "The Princeton Field Guide to Prehistoric Mammals" (2016), Chris Stringer & Peter Andrew's "The Complete World of Human Evolution: Second Edition" (2012), DK's Multi-Authored "Evolution: The Human Story" (2011), Agustin Fuentes' "The Creative Spark" (2017), and Dr. Thomas Holtz's UMD GEOL 204 "Dinosaurs, Early Humans, Ancestors & Evolution" Online Lecture Notes for information.
> 
> Attention should be drawn the work of Dr. Robert Martin concerning the evolution of childbirth and midwifing, and Dr. Daniel Lieberman's work on long-distance endurance running.


	6. Sister Species

**Summary for the Chapter:**

> From the Neanderthals to the First Homo sapiens

After a very late night with the happy and newly-expanded  _ Homo erectus  _ group, most everyone passed out from the excitement. The fire was still roaring, though much dimmer now that there was no one available to tend to it. Peridot sturs awake, giving a small yawn. She looks over to the fire, grabs some sticks, and chucks them in the center. The flames rise higher again. She turns to you, sleeping on your side, and gives you a nudge. “Hey.. psst! We gotta go” she whispers. 

You groggily get up, rubbing your eyes, and nod to her. Tip-toeing carefully, you both begin the long hike back to the time machine. “Goodness, I forgot how far we traveled. Stay close and we’ll be okay.”

It’s still dark out, and Peridot estimates sunrise will come within the next two hours. The forest is still teeming with animal sounds.

“I never expected us to get so close to those  _ Homo erectus _ !” Peridot comments, “then again,  _ they _ found us, and I may have panicked a little. Hehehe. Still, we’ll have to be more careful next time. I anticipate us spending time with more humans, we need to make sure we blend in better.”

You agree, still kinda asleep as you rub your arm. 

“At least this walk will get us up and ready for more of our adventure! We’re heading to Europe now, where humans had already settled a full 700,000 years earlier from this current time. Now, you may not have noticed since we’re hiking through a warm, tropical rainforest, but we’re currently in the middle of Earth’s latest glacial period! Beginning some 2.5 million years ago, the ice ages mark the time when the climate was cool enough for massive glaciers to grow at both poles. Throughout this time, there are the glacial periods, when the world was much colder and the ice was much more intense, and there are the interglacials, the warmer, comfortable times. Earth was toward the end of an interglacial at this time, 700,000 years ago, but we’re about to head to a time during a later, glacial period.”

After an hour of walking, you both make it to the time machine. It’s still snug between the two bushes, it’s red flowers now closed in the darkness. Taking her place back at the controls, and you yourself leaning back with your arms behind your head, she punches in a new date.

...

_ The Balkans of Eastern Europe, 260,000 Years Ago _

The cold becomes very prominent inside the time machine, and you feel like you’re back on Snowball Earth. Shivering, you peer outside the window at the landscape below. It’s a stark contrast from the humid rainforests and dry grasslands you’ve encountered so far. The mountains are very rugged and you can make out small glaciers here and there, but nothing grand. There are conifer trees scattered about the landscape, some in denser patches than others. Peridot takes the ship downwards into the jagged rocky peaks.

“Oh stars, any sleep that I had has definitely been taken away by this cold! I completely forgot the last time we were in a situation like this, so let me remedy things.” Peridot’s gem glows and she pulls out two pink sweaters. “Steven had gifted me these a while back. Even though I can produce my own heat, I find them… cute. Hopefully this one fits.” She hands you the larger of the two sweaters, and thankfully it fits you comfortably. Putting hers on, she sets the time machine to land, and it rests among some rocks.

“Okay, ready to meet some more humans?” Peridot smiles, “As before, there are multiple species of humans sharing the planet together during this time.  _ Homo erectus  _ is still going strong across Asia, and its relatives are roaming across Africa. Here in Europe, and Southwest Asia, is another species, the Neanderthals. That is,  _ Homo neanderthalensis _ . These seem to be the most familiar of prehistoric people, which makes sense given that they’re the first species Earth scientists ever discovered. Even Greg seemed to know about them, but the documentary we watched together was very inaccurate. These Neanderthals were all living in a stone house watching TV, and the big male worked this dinosaur like a crane… actually, come to think of it, that may have just been a cartoon.” 

Sheepishly, Peridot climbs out of the pod, stamping her feet into the rough, mossy ground. You follow as she walks towards the base of a tall cliffside. “I’ve located a family living in a cave a little bit away. We just have to walk carefully around this steep wall. Hopefully this time around they don’t see us.”

Taking care to avoid sharp stones or possible areas for rockslides, you follow Peridot around the cliffside. You can feel the sweater doing its work, and you feel very comfortable wrapped in its warmth even as you navigate the awkward and pointed terrain. It isn’t long before you reach your destination, and Peridot takes you behind a large stone to investigate.

“Neanderthals are one of your species’ closest relatives, only having diverged from the same common ancestor around 800,000 years ago. Both species have quite a lot in common, including key behavioral traits. As far as I’m concerned, they’re as human as any one I’ve met on Earth so far!” Peridot says, before turning back to look for any signs of the people.

Sure enough, the cave was quite populated! You manage to spot ten Neanderthals. They’re very muscular in their build, with robust arms and legs and powerful chests (everyone is wearing tawny animal skins draped around their bodies). Their faces are adorned with clear brow ridges and slightly large noses. This family of Neanderthals is light-skinned, and there is a brush of tan and red hair atop most everyone’s heads. In particular, you notice three children, an adult man, two adult women, a teenage boy, and two elderly individuals, a man and a woman. The old woman is sleeping at one corner of the cave, while the old man is sitting along a wall. A fire illuminates the inside, full of all sorts of stone tools, animal skins, grass-and-moss bedding, and other objects.

Peridot draws your attention to him. “Look at that poor guy. He’s lost pretty much all of his teeth… the left side of his face is all injured… blind in one eye, deaf in one ear no doubt. Even his left arm is broken beyond repair.” You watch as the old man uses his good arm to pull an animal skin blanket over his shoulders, his expression very blank. “You’d think he’d have been a goner a long time ago! Left to die to relieve his brethren from the burden. Not so.”

The adult man and one adult woman walk up to the elder, the woman crouching by his right side and talking gently into his ear. The man sits on his opposite side, holding a wad of cooked meat in his hand, which he begins to chew. Smiling as best he can, the elder pats the woman on the head and carefully turns toward the man, who has finished chewing and proceeds to pass the food into the elder’s mouth orally.

“Neanderthals cared for each other, just like members of your species do.” Peridot explains, “they had compassion. Your Earth scientists have found many remains of Neanderthals that have lived through injuries that otherwise would have left them vulnerable to nature. This tells us that the families looked after their sick and elderly. They even knew how to use medicinal plants: for example, they would use poplar leaves as painkillers.”

Once finished, the elderly man smiles at the younger man, who (smiling back) adjusts the skin-blanket for a cosier fit. While he stays by his side, the woman returns to another part of the cave, rejoining her fellow adult, the teenage boy, and two of the kids. They’re all preparing animal skins, holding the flesh by their front teeth and using a sharpened stone to scrape along the sides, removing any access tissue.

Right away you notice that the other adult woman has quite the accessories: she’s wearing a row of black feathers in her hair, which is held up by string into a sort of bun, and she has a necklace of what looks like an eagle’s talons. Clearly these humans have a much wider range of culture than the  _ Homo erectus  _ you met earlier. Indeed, they’re as much like you as Peridot mentioned.

One of the children runs off to check on the elderly woman, who is still lying there at the end of the cave. She gently nudges on her shoulder, but there is no movement. She calls to her, nudging harder, still no response. Eventually, she begins crying and calls to the other members of her family, who all (save for the older man, who looks over in curiosity) rush beside her. The adult woman with the feathers in her hair gently places a hand on the little girl’s shoulder, reaching over to check the elderly woman’s pulse. She’s dead.

“Oh dear… that’s tragic.” Peridot frowns, “looks like a burial is in order. Let’s give them a moment.” She takes you away towards the time machine, getting you inside for a second as she adjusts the time and fast forwards several hours. The day is nearing evening, and the sun is gradually getting closer towards the horizon, when Peridot leads you back out of the pod and towards the Neanderthal camp once again.

“Belief in something greater than yourself, that is having a religious belief system, probably predates  _ Homo sapiens _ . However, it’s one of those things that Earth scientists have trouble deciphering from the rock record. Instead, they turn to studying people living in the present day for clues as to its origins. It seems that early peoples recognized and believed in supernatural elements in their daily lives, so much so that they didn’t have words in their languages for ‘religion’, it was just life as usual (something many traditional societies today share as well). They most likely paid close attention to weather events or geologic phenomena or the intricacies of organic life and made connections to different beings like spirits or gods that intervened with them and their communities. So something like the death of a loved one would have been a natural part of these beliefs, and it is with humans like the Neanderthals that we start to see signs of this. As we’re about to see.”

Once you both make it back behind the rock and peek inside the fire-lit cave, you notice that everyone looks very different. All the Neanderthals have painted themselves with a reddish-brown pigment, having drawn different patterns on their faces and arms. “Something else that appears around this time is the use of ochre. It’s a mix of clay, sand, and minerals that early humans could use to paint with. The first members of your species will use them too, and they’ll learn how to make even more colors out of different minerals as well.” 

The adult man emerged from the end of the cave, carrying the elderly woman in his arms. With the utmost care, he gets on his knees and places her gently inside a large, dug-out pit in the center of the cave. He lays her on her left side, her legs curled up towards her stomach. He takes her arms and folds them inwards so her elbows face her chest, hands clasped together as if in prayer. One he’s finished, the man joins with the elder, who is standing beside him, holding a large stick for support. Who knows his relation to this older woman? Before long, everyone is singing.

“Gosh, if only we could understand what they’re saying.” Peridot comments. After a few minutes of song, everyone takes handfuls of dirt from the cave floor and covers the dead elder. Before long, the pit is fully covered. The smallest child, grasping a large and smooth stone, places it at the center of the buried pit.

“Wow, I never expected to see a Neanderthal burial. I feel kinda bummed. I don’t think I’ve ever even been to a funeral before… come on, let’s go.” Peridot solemnly makes her way back to the time machine, and you can’t help but give one last look at the family before turning back to join her.

…

_ South Africa, 125,000 Years Ago _

After a few quiet minutes in the time machine, you look out to see that you have returned to the familiar sight of Africa. In particular, you’ve arrived at the edge of a rocky coastline where great stones protrude into the rough sea. Further inland you make out grasslands and various forms of bushes and shrubs, some with colorful flowers or bizarrely shaped leaves. Seabirds quack and chirp in the breeze as the pod settles along the rocks.

“Finally, after all this time, we’re finally going to meet members of your species!” Peridot cheers, leaving the time machine. “ _ Homo sapiens  _ appears to have evolved around 350,000 years ago, from the same common ancestor as the Neanderthals. However, while the latter emerged in Eurasia, your species evolved in Africa. There were several intermingling populations of humans living throughout the continent, and they all shared very similar characteristics unique to their species: they had a much larger forebrain giving them an equally large forehead, a flattened face, and the first signs of a chin!”

You follow her over the rocks, moving as carefully as you were back in Europe. “I’ve jumped ahead to 125,000 years ago, and we’re currently in another interglacial period. So now it’s nice and warm, perfect for a day at the beach.” Peridot smiles. As you both stroll through the stony ground, you happen upon a collection of three  _ Homo sapiens  _ individuals relaxing on the shoreline. They’re dark-skinned and sparsely clothed, wearing garments only around their waists and limbs. In particular, their hands are patched up with fibers. The men appear to be working with a stash of seashells, and there’s a small fire going on beside them.

“Act natural,” Peridot says, “maybe we can sit behind that stone over there.” 

But it’s too late: you both have been spotted.

“Hey friends! Greetings!” one man calls. He has a fine beard and a few pigments across his face. 

Another perks up, “what brings you to the coast?” This man has no beard, instead sporting small locks around his hair.

“Oh, erm…” Peridot begins, “we were just passing through!” She nervously grins, “it’s a… nice day.”

“Yes, it is.” the third human responds, “why don’t you join us? Are you hungry?” This man, shorter than the other two, has a shorter beard but is bald otherwise.

“Um… sure! We can stay for a bit.” Peridot smiles, nudging you along as you move towards the men. One man makes room for each of you, and soon everyone is sitting together.

“We’ve been sampling today’s harvest: it’s mussels for lunch!” the bearded man grins. He picks up another shell and examines it before setting it down on a flattened stone. He takes another, smaller rock, and hits the mussel right on its valve. The shell opens and he carefully pulls out the meat, placing it in a little stash beside him. He turns to his bald friend. “Hey, this one looks about the right size. You want it?”

His friend eyes the split shell carefully, “...yeah, sure. Thanks!” he reaches over and takes it.

“So, where are you from?” the bearded man asks Peridot. “I don’t believe I’ve seen you before.”

“That would be correct! We’re from… er… the acacia forest?” Peridot says unconvincingly, to which you give a small face palm.

“Ahh yes.” replies the man with the locks, “I have yet to visit those woods. Acacias are hard to come by here. The bark produces a nice black pigment that I’ve been trying to look for, and I hear the flowers are pretty tasty.”

“Well, it’s a pleasure to meet you.” Greets the bearded man, “My name is Gamiro. Next to me is my brother Khana, and pipsqueak over there is called Noo”. The men laugh as Noo, the bald man, smirks, “go jump in the ocean Gamiro!” At that point everyone is laughing. Suddenly Peridot doesn’t seem so nervous.

She turns to you, “well, I can already tell this is going to be much easier than I thought. Speech and language of a type that modern humans recognize seems to have developed around 300,000 years ago, correlating with the evolution of  _ Homo sapiens _ . Take any one of these gentlemen back to the present with us and they wouldn’t stand out at all. They’re the same, physically and behaviorally, as people like you.” 

Peridot smiles back to the trio. “It’s an absolute pleasure. My name’s Peridot, and this is ---.”

“Peridot, huh? That’s a funny name. Don’t think I’ve ever seen anyone around here looking like you.” Khana comments. “Yeah!” Noo adds, “you’ve really gone all out with the pigments. Never knew you could get such a light green like that. What do you use?”

“Oh, um… that’s just how my body looks.” Peridot replies, looking down at her arms.

Everyone stares for a moment, seemingly confused, before they shrug their shoulders and chuckle. “That’s cool.” Gamiro says, “I shouldn’t be too surprised: most people here have different skin tones. Some of my cousins are a bit lighter skinned than I am.”

“That’s neat.” Peridot nods, before turning to you. “Genetic studies done by Earth scientists have discovered that the entire range of modern human skin pigmentation originated on the African continent, and that different variations became more prominent in different groups throughout the region. You can see this range even today.”

“So…” Khana speaks up, “who’s ready for food?” All this time, Khana had been cooking the mussel meat by the fire, and it looked just right. “Ahh, yes, gimme gimme!” Noo’s mouth watered, as Khana prepared some stone-plates. “Now now,” Khana playfully scolded, “Gamiro caught all these mussels, so he gets the first helping.”

Gamiro scratches his head and blushes, “aww, you’re too kind.”

“Oh wow! You’re a freediver? I’ve heard of people like you: able to hold your breath for many minutes while diving tens of feet into the sea!” Peridot’s eyes lit up as Gamiro receives his plate.

“Haha, yes indeed. It’s a special skill around here. Many of my clan can dive like me. Noo over there is a freediver too, but he couldn’t help today because he sprained his ankle.” 

“That darn rock…” Noo frowns, rubbing his bandaged ankle. His emotions changed as he received his plate, his stomach rumbling. “Oooh thank you.” he grins, but before he could dive in, Gamiro waggles his finger.

“Nuh uh… Noo, you know better. We have guests. They should have the first bite.” Gamiro passes his plate over to Peridot, while Khana hands you a plate. Noo just crosses his arms and smirked.

“Oh… wow, thanks!” Peridot smiled. You both take a bite, and soon everyone joins you in the feast. The saltiness of the sea adds a nice flavor to the mussel.

…

After about an hour of food and laughs, it was time for Peridot and you to depart. 

“We appreciate your hospitality! We wish you best of luck on your next freediving trip!” Peridot calls to the men. Gamiro, Khana, and Noo all smile, clasping their hands together. “May the spirits be with you.” Gamiro replied.

“Here… take this as a symbol of friendship. Our clans are bonded for life.” Noo hands you a mussel shell, but it appears to have been dried and decorated. With a series of parallel lines engraved on its surface and a splattering of pigments colored on top.

With a warm goodbye, you follow Peridot back to the time machine.

“That was nice!” Peridot says, patting her belly, “one of the most valuable assets among the first  _ Homo sapiens  _ and beyond is the ability for strong networking. Early humans not only had a deep understanding of their environment - the usefulness of different plants, where the best watering holes are, what animals are dangerous - but they also were very close with their neighbors. They may not have seen them for many months out of the year, but if the weather got a little too intense, or if supplies were low, they could always use their networks to trade and foster bonds with other people.”

You smile, holding the mussel shell securely in your hands. “That’s another amazing trait of  _ Homo sapiens _ : a heightened sense of aesthetics. We saw instances of this in other species, like the carefully stylized toolkits of  _ Homo erectus  _ or the use of feathers and talons for decoration in the Neanderthals, but it was with modern humans that the understanding of beauty and application of art really took off!”

Peridot opens the time machine and sets in new coordinates. “Just 10,000 years from now, the Earth will enter another glacial period. The last one in fact! And with the cooling of the climate imminent,  _ Homo sapiens  _ is about to face one of its biggest adventures yet!”

…

**_To be continued!_ **

**Notes for the Chapter:**

> Special thanks to Chris Scarre et al. "The Human Past: Fourth Edition" (2018), Chris Stringer & Peter Andrews "The Complete World of Human Evolution: Second Edition" (2012), & Agustin Fuentes' "The Creative Spark" (2017) for information.
> 
> Attention should be drawn to Dr. Nina Jablonski's work on the evolution of human skin pigmentation, and Dr. Eleanor Scerri et al.'s pioneering work on African multiregionalism.


	7. North, South, West, and East

**Summary for the Chapter:**

> From the Eruption of Mount Toba to the First Native Americans

_ Southwest Asia, 75,000 Years Ago _

Great stretches of white, yellow, and green appear before you as Peridot pilots the time machine far above low-earth orbit. You’re just able to make out the continents, but their familiarity quickly vanishes upon closer inspection. You quickly notice the enormous, intimidating ice sheets covering much of Europe and Siberia, and below the coastlines of much of the landmasses have expanded further outwards. The Red Sea, in particular, is now a thin lake as a small land bridge lies between the Horn of Africa and present-day Yemen. The land itself seems much drier too, with only the smallest patches of forests in the northerly regions.

“It’s crazy how much a little ice can do!” Peridot comments, taking in the view with you. “The thing about glacial periods it, having so much ice locked up at the poles means that the sea level drops significantly. In some areas, for example, the ocean is 230 feet lower than present-day levels! This has allowed large areas of the seabed to be exposed, giving rise to new lands for people to explore.”

Peridot takes the pod a little closer to the eastern Mediterranean, where the recognizable upside-down triangle of the Sinai is hidden between exposed land. 

“ _ Homo sapiens _ , like the three friends we just met, have had a long-established presence on the African continent since their initial evolution. They ranged from the rough terrain of the Atlas mountains in present-day Morocco to the warm coastlines of southern Africa. If you remember, several species of humans have made treks outside of Africa into the wider world - like  _ Homo erectus  _ or the ancestors of the Neanderthals - and your species would be no different. While there appears to be archaeological evidence of earlier treks into Eurasia as far as 200,000 years ago, the most significant journeys that left the biggest marks on your species’ DNA began around 76,000 years ago. Which is why I’ve taken you above Southwest Asia.” 

Peridot flips open a compartment on her dashboard and pulls out a small glove. Making sure it fits securely, she begins making strange, deliberate movements with her fingers. Cocking an eyebrow, you look down to see bright red marks in your field of view. Peridot has using part of the Earth’s furthest atmosphere like a giant white board!

In particular, she draws a big circle around the Arabian peninsula, with one arrow leading from East Africa across the Sinai and another across the gap closing the Red Sea. “Like the other hominins, groups of migrating  _ Homo sapiens  _ took advantage of the low sea levels to expand their ranges into new territories. They seem to have had an established presence along Southwest Asia, as Earth scientists have found tools in the Levant that date to between 194,000 and 177,000 years old, only about 100,000 years younger than the earliest remains of your species in Africa! And there are instances of tools at other places, like here in the present-day United Arab Emirates that bear a very close appearance to tools from present-day Ethiopia. So that tells us two things, at least: it confirms that the ancestors of humans in Southwest Asia came from Africa, and it shows that the conditions were just right for people to survive there for a very long time.”

Peridot highlights the patches of green and the myriad rivers radiating across the Middle East, and you have to do a double take at the presence of so much water. 

“Arabia was a much wetter place than it is today, even despite this glacial period making conditions very dry. There were always safety by the rivers and oases, where humans could hunt, forage, and fish to their heart’s content. And it also helped that they weren’t alone in these lands, because migrating  _ Homo sapiens  _ came into contact with Neanderthals here!” Peridot exclaims, pulling out her tablet and projecting an image of the Neanderthal family from before, their solemn faces returning to your memory.

“If you know anything about human genetics, you might already know that  _ Homo sapiens  _ interbred with Neanderthals - roughly around this time, actually - and that most humans alive in the present day (that do not have immediate African ancestry) have a little Neanderthal DNA inside themselves. In some areas of the genome it’s about 2.1%. That’s because Neanderthals do not appear to have entered the African continent, so their southernmost range was Southwest Asia. When members of your species began making homes for themselves there, they encountered this related species and mated with them.”

Peridot swipes the image right, revealing a map showing the frequency of Neanderthal genes in living-human populations. Africa appears mostly barren, while the rest of the continents are illuminated with color. “Now… the reasons behind this interspecies mating are… how do I put this… unclear. Was there genuine romance? Was there… erm… sexual assault? Don’t ask me, because I don’t know! The point is, that Neanderthal DNA was passed on from person to person, and was carried with the migrating  _ Homo sapiens  _ all across the continents from those moments on. In fact, there is growing evidence that the DNA from that species may have both helped and hindered the future descendants of those first encounters. I remember reading a recent study a while back that mentioned that Neanderthals might have introduced the capacity for red hair among European peoples. Now that’s awesome!”

You nod your head in agreement as Peridot moves the time machine further away from Southwest Asia, nearing the Indian subcontinent and Southeast Asia. You immediately notice that Sri Lanka is now connected to India by a strip of land, and the islands of Southeast Asia are now connected together within one single landmass. Along the way, Peridot is using her glove to make a series of arrows pointing eastward along the continents.

“Eventually, however,  _ Homo sapiens  _ populations would grow ever so slightly, and they began to make longer and longer journeys away from their ancestral homeland. By 75,000 years ago, where we’re at in time and space, they seem to have reached as far as India and perhaps started trickling into Southeast Asia as well, where  _ Homo erectus  _ was still living.” 

Peridot looks over to you, giving a small chuckle at your expression. “Yeah, I know, it’s weird to see Indonesia and Malaysia and Thailand all bundled together, but again, that’s just how it is during a glacial period. Sea levels are low and land bridges form. It’s happened several times before this… how do you think those  _ Homo erectus  _ got to Java in the first place?”

You shrug your shoulders: there’s no arguing with a time-traveling gem, not after all she’s shown you already. 

Thick plumes of smoke begin emerging from where present-day Sumatra would be located, and it isn’t long before horrifying fireworks of lava begin shooting from the area. It seems a massive volcano has erupted, heralded in by crackles of lightning from the growing smokestack.

It catches both you and Peridot off guard. Taking the helm, Peridot drives the pod for a much closer look. “Ooh boy… I nearly forgot about this.” Her voice trembles, and you can’t help but feel her shock as well.

“The source of all that destruction is Mount Toba, a large supervolcano that appears to have erupted 75,000 years ago… and we’re right here to witness its birth,” Peridot explains. “Through the course of its eruption, Mount Toba will release over 18-and-half miles of ash into the atmosphere, sending an aerial tsunami of thick, choking clouds over much of southern Eurasia.”

You both watch silently as the volcanic ash begins to travel in the breeze, covering parts of Southeast Asia in darkness. 

“For the humans living on Earth, and all the other organics for that matter, it must have been a difficult time. Large volcanic eruptions like these can have devastating effects on ecosystems hundreds or even thousands of miles away. There is genetic evidence of numerous population bottlenecks occurring during this time among large mammals, where vast numbers of organics die out, leaving only a handful of survivors to carry on an impoverished gene pool. This included big cats and great apes, including human beings. For the humans who had called Eurasia home for hundreds of thousands of years, it was a rude intrusion into their secure lives. For the  _ Homo sapiens  _ who were just starting to call the continent home, it was an unexpected roadblock. And yet…”

Peridot moves the dial on the dashboard, causing time to fly by rapidly. The dust and ash from the Toba eruption envelopes large parts of Eurasia and even manages to trickle into Africa, and eventually it dissipates until land is visible yet again. It is now 74,000 years ago.

“And yet, humans are survivors!” Peridot continued. “ _ Homo sapiens _ , as well as the Neanderthals and all the other species of humans, made it through the catastrophe. Earth scientists have found rock layers in many parts of the world showing tools found below and above the layers of soot left by the volcano: meaning that people managed to either weather out the conditions or leave for greener pastures and return back home.”

Peridot takes a moment to point at your clothes. “And these may have helped too. Believe it or not, humans seem to have developed full-body clothing around the time of the eruption. The source of this information to researchers came from a very unique place. Care to guess?”

You mull it over for a bit before waving a hand in defeat.

“Oh don’t be such a nit-wit… hey… nit. That’s it, actually!” Peridot chuckled, slapping her knee.

Her retort begins to make sense, and you resist the urge to cringe.

“Yeah, that’s right: lice!” Peridot grins, “a very fascinating study found looked at two kinds of lice, those that live in head hair and those that live on body hair and lay their eggs in clothing. These lice belong to the same species, and by comparing their DNA, it was revealed that the two split off from a common ancestor around this time. That means, at some point before then, humans started making clothes to protect themselves from the elements. The lice living on their bodies had to adapt, and some started living permanently on human hair. How’s that for interdisciplinary studies?” 

You just rub your arms trying not to think about the bugs as Peridot punches in a new time on the machine. “Hehe, try not to think about it too much.”

…

_ Off the Shores of Northwestern New Guinea, 65,000 Years Ago _

Vast stretches of blue, occasionally dotted by small green islands, appear beneath the time machine as Peridot pilots onward. A pod of dolphins breaches past and there are plentiful seabirds fluttering about. It looks like a tropical paradise, despite the fact that you are still technically within the last glacial period.

“After making it through the Toba Eruption,  _ Homo sapiens  _ continued to expand its range further and further across Eurasia,” Peridot begins. “They traversed all the way down the greater landmass that contained the islands of Southeast Asia, which your Earth scientists have named “Sundaland”, after the continental shelf that remains today. You might be thinking, ‘but sooner or later they would reach the sea. Then what?’ Well,  _ Homo sapiens  _ did what  _ Homo sapiens  _ does best, adapt and innovate! We should be meeting these intrepid adventurers right about… now!” 

As if on cue, the time machine emerges next to an enormous fleet of wooden boats, made from dugout tree trunks. Each one is piloted by several rows of people, singing as they synchronize their spoon-like paddles through the water. They wore very sparse clothing over their dark-skinned bodies. On one enormous boat in particular, smack in the front of the procession, is being led by a group of elders who are encouraging everyone on. “You’re doing wonderful everyone!” one of the leaders calls, a strong, well-built man. Another, a woman with graying hair, smiles brightly, “we’re so close! I can feel it!”

Peridot turns to you as she rests the pod in the water’s surface, the legs projecting out and spinning in such a way as to turn the craft into a vessel itself.

“The very first voyages out into the open seas were conducted by these brave individuals. By this time, 65,000 years ago, they had developed aquatic technology in the form of boats! Taking note of the environmental conditions, and using their knowledge of the winds, seas, and skies, they island-hopped down the northernmost islands beyond Sundaland towards for a new life. We’re following them to a landmass that only existed because of the drop in sea levels: Sahul, comprising of the lands that are known today as New Guinea and Australia. So these people will become the ancestors of the indigenous Papuans of New Guinea and the Aboriginal Australians! Let’s go see how the trip is going.”

Peridot pilots the pod around the fleet and pulls up right beside the lead boat, lowering the window for a moment. 

“Good afternoon!” she calls, waving, “How's the water?”

The elders look upon the green vessel not without curiosity before one of the elders replies joyfully, “it’s beautiful! We’re making good time! The currents seem to be in our favor and there are plentiful signs of life. We should be reaching our destination within the hour.”

“Sounds great! We’ll meet you there!” Peridot responds, rolling the window back up and zooming forward with great speed. Two of the kids on a neighboring boat look on with wide eyes and shock. “Wow!” they cry, “now that’s boating!”

Peridot sails on, resting back as the time machine moves forward. “Earth researchers suspect that a trip like this was a planned event, because to risk a trip like this would have been substantial. Of course, indigenous peoples know their world better than most, so they would have been able to understand the seas fairly well and be able to deduce where other lands would be. It’s been estimated that over 1,300 people made this trip, just enough to ensure that there would be plenty of healthy families to start their new lives in Sahul. What’s especially interesting is that some Aboriginal Australian nations in the far north of the continent have oral traditions that tell of their ancestors arriving from the sea. One in particular, from the Gunwinggu nation, tells the story of one of their earliest mothers arriving from a northwesterly route towards present-day Indonesia. Genetic studies have only added further evidence of these memories! Indigenous groups in Australia go a long way back, and it’s so fascinating how much they’ve retained of their distant heritage.”

The ride to Sahul is a relatively smooth one, save for a moment when Peridot’s pod almost smacks into a breaching whale, but eventually it arrives at a very pristine, sandy beach off the coast of what will become the island of New Guinea. You both exist the pod, stretching your limbs and breathing in the moist tropical air.

Peridot pulls out her tablet and selects a particular image of a rather robust jaw bone. “Check this out!” she calls, ushering you closer to the screen. “This is the fossilized jawbone of a particular species of human called a Denisovan. We don’t really have time to go visit them, but I wanted to bring them up because they’re pretty relevant to our incoming arrivals. Do you remember how I mentioned that  _ Homo sapiens  _ interbred with Neanderthals?”

You nod your head, taking a good look at the image. “Well,” Peridot continues, “they also interbred with Denisovans! That species in particular is still a very mysterious one: Earth scientists uncovered their DNA from remains found at a site in Siberia and discovered that, although they were close relatives of Neanderthals, they were very distinct from any known species of hominin then found. A brand new species, discovered because of DNA! When they compared that to populations of people around the world, they found a notable percentage among the peoples of Eurasia, with the highest counts among the indigenous peoples of New Guinea and Australia, and on to the Pacific islands. Not only that, back in Africa, they’ve also found evidence of interbreeding between  _ Homo sapiens _ and other mystery humans! Species we know even less about than the Denisovans!”

Peridot jumps in excitement. “Gosh, just think about it! A world full of different species of humans, all meeting and interbreeding with each other. Straight out of a fantasy novel I tell you!” She collects herself for a moment, “but of course, it’s no fantasy. Human evolution is a very tangled and complicated thing… your species is the end result of a vast network of different species and populations all meeting up with each other. It’s like… to be human is to also be Neanderthal, or Denisovan. Wow.”

The sound of distant cheering heralds the arrival of the fleet of boating humans. They’re just visible beyond the shoreline.

Taking note, Peridot puts away her tablet and calls you back inside the time machine. “We’d better let them have their celebration. It’s a whole new world for them! The descendents of these brave peoples will settle throughout Sahul, making homes in the lands that will become New Guinea, and some of them will move southwards towards future Australia. There they will meet a whole host of strange and enormous animals: giant kangaroos, wombats the size of rhinos, great flightless ducks, and the terror that is  _ Varanus priscus _ , a monitor lizard that could have grown three-times longer than a komodo dragon! Yeesh.”

Punching in new coordinates, the time machine begins to levitate into the air. “Eventually, as the last ice age began its slow meltdown, sea levels will rise up and begin to swallow much of the exposed shorelines, and by 25,000 years ago Sahul will have officially broken up into New Guinea and Australia. We’ll be sure to examine their future lives later on. For right now, let’s head westward to see how the other members of your species are fairing!”

In a flash of light, the time machine vanishes.

…

_ Present-day France, 30,000 Years Ago _

The time machine reappears within the thick blanket of a passing blizzard. It’s very dense and even with the bright headlights on you can’t make out anything. Peridot checks her scanners and moves the pod carefully through the snow, passing by a few rows of pine trees and lichen-covered boulders. You don’t waste time pulling on your sweaters.

“Yerragh! Curse this snow! How on Earth does Steven enjoy this stuff?!” Peridot fumes, fidgeting with her sweater has she raises her body temperature. “Hopefully I can get us out of here in one piece.”

Eventually, Peridot manages to maneuver the time machine out of the blizzard, which passes behind you like an ominous dark raincloud. She lands the pod down by a grove of spruce trees at the edge of a valley, securing it firmly in the compact snow. You emerge from the machine alongside Peridot, and you can’t help but shiver. 

The sound of rumbling footprints can be heard from behind the trees, causing a few white hares to scurry away. Peridot pushes you behind her as you both lay low by the time machine. A rough trumpet blares through the air as a small herd of woolly mammoths marches past. Two calves stay close to their mothers, trying to keep up. They’re impressive and intimidating animals to behold.

“Shh… you definitely don’t want to spook them.” Peridot whispers, putting her index finger to her mouth. “Elephants are dangerous.”

Soon the herd has moved far enough away for you two to emerge in the open. “Phew! That was close!” Peridot breathes. “Well… here we are on the eve of the harshest glacial period yet, when the ice sheets of the north were beginning to creep to their furthest extent. It’s a harsher world, but humans have been able to adapt and take advantage of every opportunity available.”

Peridot pulls out her tablet, making sure no snow falls on it, and pulls up a map of Europe. “The humans who were setting off for Sahul belonged to a particular wave of people who had been slowly making their way eastern since 76,000 years ago. As conditions changed since that time, more and more groups started moving in other directions, and one wave that started in Southwest Asia had begun to move northward around 45,000 years ago. Some of these people headed east towards Central Asia, while another kept going west until they reached Europe. These were some of the first  _ Homo sapiens  _ to enter that subcontinent, and they too came face to face with Neanderthals, just like in Southwest Asia! However… things wouldn’t stay the same forever.”

Putting away the tablet, Peridot begins slowly moving down the hillside and, glancing back at the time machine, you follow her hesitantly.

She continues, “environmental conditions worsened as the years went on. A slow-moving glacier here, an erupting volcano there, soon the area became a very hostile place to live in. Though the direct cause is unclear, the last of the Neanderthals went extinct by 37,000 years ago.  _ Homo sapiens _ , on the other hand, would luck out, remaining the only human species left in Europe. The continent was now there’s, and they soon settled into several different cultures, all of which were traditionally referred to as ‘cro-magnons’ by researchers.” 

A howl interrupts Peridot’s lesson, causing the two of you to slowly turn around. There is a lone wolf standing at the top of a hill, giving its full attention to you both. Sheepishly, Peridot raises her hands up. “Eh… nice doggy.”

Emerging from behind the wolf are several human hunters. Dark-skinned, dressed in tailored furs and skin-lined boots, and with pulled-back hair, the group takes notice and slowly approaches the two of you. There are five men and two women, as well as three other wolves with them, and they look exhausted.

“You there!” one of the men calls, his voice deep and commanding. 

“Er… yes, sir?” Peridot replies, clasping her hands together nervously. You place a hand on her shoulder to calm her, but you don’t let your guard down.

“What is your mission? Are you hunters, gatherers, or travelers?” the man continues, pointing his finger right at you.

“Just travelers! We’re passing through, that’s all.” Peridot manages to say, grinning awkwardly.

“Oh lighten up Itzal, maybe they can help us?” a woman chimes in, her features a bit cheerful. She turns to you, putting her hands to her knees, “Say, would you happen to have seen some mammoths pass through here? We’ve been tracking them for weeks.” 

“Weeks? Oh jeez, that sounds rough.” Peridot comments.

“Definitely, and trying to out pace that blizzard wasn’t fun at all.” another man adds, his facial hair a bit unkempt. “Usually we stick to reindeer, but unfortunately the herd seemed to have slipped past us a few weeks back, and the conditions haven’t been favorable to find them. By brother Argider and his dog were the first to spot the mammoth herd, so we’ve been trying to keep up with them ever since. This will be our last chance for good food before the winter reaches its harshest.”

“Well, you’re in luck!” Peridot chimes, smiling, “there was a whole herd of them that passed by over in that direction. Come on, we’ll show you!”

Leading the way, Peridot backtracks a bit to the spruce grove and the hunting band follows her, including a reluctant Itzal. Sure enough, there on the ground is a set of fresh, deep tracks.

“Well I’ll be!” one of the man cheers, “these are practically brand new!”

“Indeed. Well done… eh…” Itzal turns to you and Peridot, raising a friendly eyebrow, “who are you, by chance?”

“Oh, my name is Peridot, and this is --”. She introduces you courteously, earning a round of handshakes and pats on the back from the hunters.

“There isn’t time to lose! Let’s go, hyeah!” Itzal barks, causing the wolves to pursuit in the direction of the mammoths. The other hunters follow, but the cheerful woman stays behind for a moment, turning to you two. “Come with us! We could always use extra help!”

“Eh, why not, I’m sure you could use the encouragement.” Peridot chuckles.

Pretty soon, just like in Java, you and Peridot are joining a group of prehistoric hunters. You traverse along the edge of the valley, taking in the view. This is a relatively featureless world: mighty glaciers can be seen far into the horizon, and the land is barren and grassy save for the hardiest patches of trees. 

“While big-game hunts and harsh blizzards are exciting thrills, life for Ice Age Europeans was a relatively stable one. In much the same way as those earliest  _ Homo sapiens  _ in Africa, groups of people in Europe were connected together in a patchwork of trade-routes, often punctuated by semi-permanent campsites. However, for much of the year these peoples would have kept to themselves, living off their hard-won resources at the campsites for many months out of the year. There they could construct their weapons, or sculpt bone jewelry, or make new clothing, or even tend to those little furry babies.” Peridot gestures towards the wolves, who are intently sniffing the ground for any signs of the mammoth’s movement. 

“The first domesticated animals were dogs, originating from gray wolves that lived throughout Eurasia. Though the remains of domestic dogs predate other kinds of livestock, we don’t exactly know when they were first raised by human hands. DNA studies tell us that dogs split off from wolves sometime between 40,000 and 20,000 years ago, and there are tentative archaeological remains that seem to show dogs distinct from wild wolves, but we can’t say for sure. And just how did humans and wolves come to live together? Maybe the smell of easy meals attracted some wolves to campsites… who knows! What is interesting is that both humans and wolves are highly social animals that work together, so however they met they would have been able to understand each other on an intimate level. Dogs became ‘man’s best friend’ somehow.”

“I see them! Everyone stay low.” Argider calls, his arm waving as a signal. The whole hunting squad sinks to the ground, and slowly crawls towards the edge of a hill. Sure enough, there the mammoths are, resting and foraging at the bottom of a valley. They use their great tusks to brush away the snow, revealing yellow-green grass.

“What’s your plan?” Peridot asks Itzal, who is so passionately focused on the mammoths. 

“Normally we would go after a calf, because the cows can be very dangerous, but desperate times call for desperate measures,” Itzal responds calmly. “We’re going to need to separate one of the cows from the herd: she has enough flesh to sustain us for many months. Not to forget that her bones would be good to make new shelters, and we could always use new skins and furs.”

“I see… well, hmm.” Peridot surveys the area, honing her eyes towards a narrow cut existing the valley, flanked by rocky cliffs. “I think I have an idea,” she whispers.

“Ooh, ooh, what is it?” the cheerful woman responds, nudging at Peridot.

…

“All my research on prehistoric peoples has led to this decisive moment… this is gonna be great!” Peridot grins as you stand alongside her at the very top of the cliff. There is a very intimidating set of boulders lined up in a row, which Peridot had to carefully position using her gem tech. 

You both look down the steep cliffside to see a great commotion has gone underway. The mammoth herd has been spooked and is currently going off in several different directions. Many of the hunters, yelling and thrusting their wooden spears, are trying hard to separate one of the smaller cows from the herd, but a large cow has nearly trampled a few of them. It swings its massive head from side to side, bellowing out an angry trumpet.

You and Peridot watch with anticipation. 

Eventually the hunters manage to drive the herd closer and closer to the depression, with the selected cow charging after Itzal in particular. He desperately tries to run as fast as he can, zigzagging and dodging with all his might.

“Come on… come on…” Peridot whimpers.

Soon the small cow is right where she needs to be. With a push of a button from a pocketed device, several controlled explosions send the boulders flying down the cliffside. The hunters flee for safety, and the other mammoths stop in their tracks. With near perfect alignment, the rocks land right on the mammoth’s head, shoulder, and rump. The great elephant collapses to the ground, mortally wounded. The hunters cheer with delight, their chase is finally over.

“Yes!” Peridot cheers, earning a double-high five from you. “Come on, let’s head on down!”

As the two of you carefully travel towards the bottom of the valley, the mammoth herd stays a good distance away, observing their fallen companion as the hunters get right to work defleshing the beast.

“That was great!” Some of the hunters rush off towards you and Peridot, having finally made it to the kill site. They wrap you in big hugs, and one ruffles Peridot’s hair, earning some comedic complaints from the gem. 

They invite you over to observe the mammoth: this is perhaps the closest you two have gotten to a long extinct animal since your travels in the Mesozoic. It is not much larger than a modern elephant, but the curved tusks and massive shoulder hump make it a notably distinct creature.

“Peridot… how on earth did you manage to work those boulders?! No offence, but you’re kind of a songbird.” Itzal exclaims, digging his stone blades into the mammoth with a grin.

“Eh… let’s just say I know a thing or two about the hunt… nehehehe.” Peridot blushes, rubbing the back of her head.

“Well, I’ll tell you this much, you’ve been a great help. Thank you so much! Our people will not rest hungry for a long time.” Itzal compliments, giving her a bow.

Peridot returns the bow, taking a look at her watch. “Oh jeez… well, this has been a great, and I appreciate your camaraderie, but I’m afraid we need to get going.” 

“We absolutely understand… your campsite must be very far away,” the cheerful woman replies, walking up to you both with Argider. 

“You could say that.” Peridot winks to you. You can’t help but grin at that.

“Well, you’re going to need this… I couldn’t help but notice you were lacking in any protection. There are lots of lions, bears, and hyenas out there that wouldn’t think twice about snacking on you.” Argider hands you a well-made, wooden spear. It is tipped with a very sharp blade made from reindeer antler. You admire its craftsmanship.

“Ooooh that’s so cool.” Peridot’s eyes light up.

“And… here’s a little something something to remember us by.” The woman hands Peridot a small stone sculpture. Upon closer examination, it looks like a plump woman with exaggerated sexual features.

“Wow! Thanks!” Peridot smiles, looking over the figurine. She turns to you, “this is what’s known in the archaeological literature as a Venus figurine. They’re almost always depicted as curvy ladies… but we don’t really know just what they were used for. These figurines highlight a greater presence of artistic expression throughout Eurasia during this time… oh I wish we had time to see some cave paintings!”

You two spend some more time saying goodbye before making the slow trip back to the time machine.

…

_ Present-Day southern Alaskan coast, 19,000 Years Ago _

You have been in the time machine for several hours now. You look below to see the icy, rocky coasts of the Pacific Northwest passing by as Peridot pilots the pod. She lazily watches the shoreline as she continues her story.

“Even through the harshest periods of glaciation,  _ Homo sapiens  _ continued its movements across Eurasia. By the same time of our adventures in Europe, 30,000 years ago, they had managed to reach Siberia from Central Asia. Only a few tens of thousands of years later, they reached the most easterly part of Eurasia, where they came into contact with populations of  _ Homo sapiens  _ who had been moving northward from East Asia. They hooked up, and around 24,000 years ago they became isolated in a new land called Beringia.”

Peridot once again pulls out her tablet, showing a map of Asia and North America. There is a thick patch of land, larger in width than all of mainland Europe, connecting Siberia to Alaska.

“This was another result of the drop in sea levels following the rise of glaciers. The land between the two continents of Eurasia and North America became exposed and turned into a cold expanse of grassland, where mammoths, deer, and other animals made a home for themselves. With plenty of plants and animals to rely on, humans were able to survive here. However, because they were isolated from the rest of the world for so long, they developed their own unique genetic signature.”

You do a double-take as you look out the window to see a small fleet of vessels patrolling the waterways. They were dugout boats, similar to the ones the ancestral Australians were using, but the people who piloted these boats looked different from most of the humans you’ve seen up to this point. Their skins were much lighter, almost copper-colored, and they wore their hair in beautifully done knots. Their clothes were highly decorated with different pigments. 

“Do they look familiar?” Peridot quips, smiling. “The people who were isolated in Beringia would become the ancestors of the Native Americans.” 

You watch as the boats sail past, but Peridot doesn’t go in for a closer look this time around.

“It has been a big question in academic circles for many decades about how the Americas were peopled, but thanks to recent work we’ve been able to get a better understanding,” Peridot explains. “There is a growing body of evidence that the first Americans arrived via the sea, taking boats and heading south of Beringia along the Pacific coast. There were plenty of riches along the way, vast fields of kelp forests teeming with animals, so these people could have ready access to food. Over the next few thousand years, people began settling along the coastlines, making it as far as the southern reaches of South America in record time. It wouldn’t be until 14,000 years ago that the Americas had begun to be densely populated from coast to coast and by that time all of the Earth’s major land masses were settled by  _ Homo sapiens _ , the last remaining species of humans.”

You take in her words with a heavy sigh as Peridot punching in new coordinates. She hears your solemn breath and turns to you with a small smile. “Hey, don’t fret. Remember, there may not be any Neanderthals or Denisovans walking around anymore, but their genetic legacy lives in throughout the world. There is probably more DNA from these extinct human species in the present day than there has ever been throughout the many hundreds of thousands of years they existed. I think that speaks for itself.”

…

**_To be Continued!_ **

**Notes for the Chapter:**

> Special thanks to Chris Scarre et al. "The Human Past: Fourth Edition" (2018), Donald Prothero's "When Humans Nearly Vanished" (2018), & Brian Fagan's "Cro-Magnon" (2012) for information.
> 
> Attention should be drawn to Dr. Michael Bird, Dr. Corey Bradshaw, and et al.'s work on the peopling of Australia, and Dr. Jon Erlandson et al.'s pioneering work on the Pacific Coastal Hypothesis for the peopling of the Americas.


	8. An Entirely New Epoch

**Summary for the Chapter:**

> From the Extinction of the Ice Age Megafauna to the Birth of Agriculture

_Present-Day New Mexico, 12,000 Years Ago_

“By now the world’s situation should be familiar to you.” Peridot begins, using a comedically dramatic voice. 

You both are flying across vast expanses of prairie, passing by herds of horses, bison, and camels grazing in the fields, with the occasional mastodon strolling by. It’s still noticeably cold, but being this far south there are no massive glaciers to be seen, though there are the occasional groves of broad-leaved trees in the distance.

“For the past 88,000 years or so, Earth had been experiencing its last glacial period, or ice age,” she continued. “All across Eurasia and North America, enormous 2-mile thick ice sheets covered the northern reaches of the continents, creating a dry world with only the sparsest pockets of warm-weather vegetation towards the equatorial regions. Sea levels were at an all-time-low, exposing vast stretches of the seabed, giving rise to great lands like Sundaland and Beringia where humans and other organics could live. But things were about to change.”

Peridot rests the time machine on solid ground, right by an enormous patch of white-petaled flowers. She opens the pod and takes in the cool air. You find yourself clutching to your sweater, silently hoping for warmer weather.

“Earth’s global temperatures started to rise around 20,000 years ago, just as the ancestors of Native Americans were beginning to trek south into new lands. Peoples around the world, particularly in the Northern Hemisphere, had begun to notice all the weird changes as they went about their hunter-gatherer lives. Summers started getting longer, winters noticeably shorter. Glaciers were retreating, exposing new territories to explore. Animal and plant distributions slowly changed as cold adapted species shrunk towards the glaciers, while warm-adapted species expanded their ranges upward. And all of this accelerated until 15,000 years ago, when the climate of the Earth had nearly reached something we would recognize today.”

Peridot reaches down and picks up some of the wildflowers, gently holding them in her hands. She gives you some, which you instinctively bring to your nose to sniff. They smell kind of like clovers.

“These little flowers are called white dryas. They’re the namesake poster-children of a brief period in Earth’s history called the Younger Dryas,” Peridot explains. “By 13,000 years ago, so much water had melted from the giant glaciers that it started to affect ocean currents. The Gulf Stream, a current in the Atlantic Ocean that moves warm tropical water up north, had received so much of the icy-cold meltwater from the glaciers that it became very weakened. Without this major current spreading warm water to the north, things suddenly got very cold again within 200 years! It was like another mini ice age! The white dryas flowers like cooler conditions, so they spread out across Europe and North America during this time, hence the name.”

Nodding your head, you hand the flowers back to Peridot as you observe the area around you. A group of Native Americans is moving through the landscape about a couple hundred feet away. Dressed in close-fitting skins, some of the men are carrying noticeable wooden spears, while some of the children are holding small edible plants they had gathered. 

You nudge Peridot’s shoulder, bringing her attention to the people.

“Ooh! Nice work! You spotted some Clovis people.” Peridot exclaimed, grinning. “They’re one of the many regional cultures that developed following the peopling of the Americas. Earth researchers have found their stone-tipped points all over the continental United States. In fact, I’ve taken us to the site where they were first discovered. This place will one day be a city called Clovis, New Mexico.”

Peridot begins making motions reminiscent of a human using a spear. “What’s really neat about these guys is that they often went after big game animals. Their ancestors had already been living and exploring the continent for a few thousand years now, so they had gotten very familiar with the local organics. To go after all the new prey animals, they developed a neat device called an atlatl.” 

Peridot pulls out her tablet and shows you a picture of one. It’s a blunt, elongated object with a little divot at the end. “They’re spear-throwers! All you have to do is attach the base of your spear to the little hole at the end, and then you launch it. These babies were much more efficient at hurling spears than a man using his bare arm. They could increase the range of a throw by a few hundred feet! Other peoples in Europe will develop the same technology too: it seems to be a response to the changing world.” 

The two of you decide to get a little closer to the group of Clovis people, who are now cautiously maneuvering around a pair of ground sloths emerging from a burrow. The slow animals look over at the humans with a careful eye, bearing out their massive, clawed paws just in case. One mother clutches her two kids close, while one of the men scowls at the animals.

“A changing the world is indeed. No doubt you’ve become quite familiar with all of these different ice age mammals? All the mammoths and sloths and saber-toothed cats?” Peridot asks, to which you nod and shrug your shoulders. It’s kind of hard not to notice such large animals.

“Well, take one last look, because they’re all about to go extinct. In a few hundred years, following the end of the Younger Dryas and the continuation of global warming, many of the world’s large animals or megafauna will die out. And it’s a process that’s taken many thousands of years across different places… let me explain.”

Peridot brings you back to the time machine and pilots it upwards, giving you a good view of the herds of mammals. 

“So, just to recap real quick.” Peridot turns to you, setting the time machine on autopilot. “ _Homo sapiens_ had evolved in Africa around 350,000 years ago. From there, in successive waves, they expanded their range into Eurasia, with the largest movement occurring some 76,000 years ago. They reached Australia by 65,000 years ago; Europe by 45,000 years ago; and the Americas by 19,000 years ago. During all that time, they encountered animals of all different kinds, and many of them were not used to human beings. This was particularly true in places where hominins had never evolved, like the Americas or Australia. As people started growing in number and becoming more familiar with their local environments, they began to have an effect on the organic life already living there.”

You look out the window to see a few mammoth kill sites, not unlike the one you both participated in back in Europe. Some have already been abandoned, having been stripped of the essentials.

“There is a curious correlation between the arrival of humans in certain continents and the disappearance of the megafauna native to those regions. Here in North America, for example, many of the large animals had died out by 11,000 years ago. Native Americans had already established a presence here by 19,000 years ago (as I mentioned earlier), but it wasn’t until 14,000 years ago that they became widespread and well-adapted. Incidentally, it’s not long after that many of the populations of mammoths, horses, camels, sloths, and big cats started declining. A similar thing happened in Australia: after humans began trickling down into the continent from the north, they spread out and came into contact with more and more animals. All those giant kangaroos and wombats and lizards I told you about. Humans become widespread in Australia around 45,000 years ago… and sure enough almost all of the giant animals died out by 40,000 years ago.” 

Peridot continues, “Earth researchers have argued about this for a long time, but given these observations it seems that humans played a major role in the extinction of much of Earth’s megafauna. And it’s in the Americas and Australia where this is most prominent! Since _Homo sapiens_ , and other human species for that matter, had been living in Africa and Eurasia the longest, the animals there had plenty of time to get used to a human presence. They were able to, for the most part, adapt to the actions of human hunters. The arrival of humans in Australia and the Americas was so brief that the megafauna there had no time to adapt… so off they went.”

Giving a small “hmm”, you ponder over the matter, before Peridot punches in new coordinates.

“It’s good to remember that the megafaunal extinctions might have been very complex and different in many parts of the world. Some of the species losses could have had more to do with hunting, and others with climate changes like the Younger Dryas. Or perhaps a combination of those factors just made survival difficult and exacerbated the remaining populations. It’s a fascinating debate… regardless of the ‘whys’, when the last ice age drew to a close 11,700 years ago, everything had changed. A new epoch had dawned.”

…

_Japanese Archipelago, 11,700 Years Ago_

Exiting the time machine, you take in the cool, comfortable atmosphere. Peridot had landed the pod near a meandering stream, located within a lush, green forest. Oaks, pines, beeches, and chestnut trees surround you, providing shelter to many smaller bushes and tall grasses. A regal, spotted deer notices the two of you and sprints off into the woods.

Peridot, surveying the area, begins to lead you onwards, parallel to the river. 

“When I meant that a new epoch had dawned, I really meant it. Remember a while back when I explained the geologic time scale? How Earth’s deep history is divided into successive stages?” Peridot asks, to which you nod your head and give a thumbs up. “Excellent!” she beams. “Well, since eras are divided into periods, periods are divided into epochs. 11,700 years ago, the Holocene Epoch started! That’s the age that encompasses everything up to present times. The previous 2.4 million years or so - that is, the time of the Ice Ages - is called the Pleistocene Epoch. What’s really funny is that the names for the different epochs of the Cenozoic Era are rather literal. Pleistocene means “most new”, while Holocene means “entirely new”. And that is a remarkably accurate assessment of the world we’re in right now.” 

Brushing past some bushes, you take note of some melting patches of snow along the ground. Seems as though winter is on its way out. Coming across some large rocks in your way, you help Peridot over them by holding her hand.

“With… eugh, dumb rocks…” Peridot fumbles, “with the last glacial period finished, the Holocene is reserved for the following interglacial period. All of the previous interglacials of the Ice Ages are considered part of the Pleistocene. What makes the Holocene so special is that humanity is still living during this interglacial period, and so much cultural development has occurred within it. But, really, from a geologic point-of-view, the Holocene isn’t really that special. Still, we’re concerned with human history right now, so it’s quite a notable time. At the epoch’s beginning, the Earth’s climate and surface underwent a mega-boon of change. Temperatures around the world warmed significantly, and the sea levels continued to rise following the melting of the great glaciers. Some parts of the continents, like the lands of Beringia and Sundaland, were swallowed up by the sea, while others rose upwards as the massive weight of the glaciers was relieved. With warmer temperatures becoming a norm, plant life spread out across the Earth’s surface, colonizing land near the poles and forming great forests at the midlatitudes.”

Before long, the river splits in two, and Peridot halts. She’s taken you as far as she wants. At the bend in the river stands a rather steep cliffside with a large cave at the center. You notice some significant human activity around the outside: there’s a great fire-pit at its center that is being tended to, and several groups of people are working with food and natural materials. Many of the men are sporting handsome facial hair, and everyone is dressed comfortably in skins. 

“Humans were left with a much different world than they knew during the Ice Ages. For people who had spent generations living along the coast, they had to watch as their shoreline moved many miles away from them. And groups living along the barren, glacier-bordered plains of the north eventually found themselves living in a forest! Thus, human populations began to adapt to these changes in brand new ways, with techniques that would have proven utterly useless to their ancestors before them.” 

Peridot points to a teenage boy, tying some sinews together and placing the ends across an elongated stick. “With nearly all the megafauna gone, the only game animals left were small, sprightly creatures like deer, pigs, and rabbits that could run and hide in the woods. It no longer made sense to go after them with big spears, so forest peoples across the world developed the bow-and-arrow. It was light-weight, much more easily portable, and could target prey with even greater accuracy than an atlatl.”

Taking everything in at once, Peridot takes a seat and begins playing with the pebbles around her. You watch as she begins sorting the rocks into groups.

“For some groups, like the humans I’ve brought you to see here, environmental conditions became so favorable that they decided to change the old ways of living. Instead of a life moving with the herds, bordered by a few weeks or months at a temporary camp for rest and work, people figured that they could stay permanently to one place.” Peridot has now placed some of the pebbles into little piles, while leaving others alone. “The end of the last ice age created many regions around the world where there was a great abundance of resources within fair distance of each other. Humans could settle down and take advantage of an almost readily available supply of food, water, and building materials. Many of these places include forest clearings or the edges of riverbanks, like this one. And with so many materials available to support them, human groups simply grew in size!”

“Once such place is here, within the Japanese archipelago.” Peridot explains, gesturing to the area around you. “During the Ice Ages, the islands that would become Japan were composed of a single strip of land, connected to the greater Eurasian continent. Humans first reached these parts 32,000 years ago, and remained here as sea levels eventually cut them off from the mainland. By 16,000 years ago, the descendants of these people developed the first cultural complex of Japan, the Jōmon. It is with people like these that we see the start of sedentism: staying in one region permanently and building a life there.”

You and Peridot observe a group of Jōmon people working with what appears to be clay. Rolling pieces up into long, tubular wads, they start coiling the clay-tubes together in a circular pattern over a flattened, clay base.

“By staying in one place, humans could begin to tinker and experiment with new technologies that proved to have immediate and effective uses. Starting in East Asia 20,000 years ago and in many independent sites around the world much later, sedentary peoples invented pottery. Previously, foragers had weaved containers out of natural fibers to carry small items around, but baskets like those don’t usually last a long time. With pottery, not only could you store items much longer, if you made bigger pots you could keep even more items in storage! And, given that clay pots had to be fired before use, they were durable and useful for cooking meat and foliage and boiling seafood! Jōmon peoples even decorated their pots, using cords to imprint beautiful designs along their surfaces: that’s where the name Jōmon comes from, ‘cord-pattern’.” 

Getting up, you follow Peridot as she begins the small trip back to the time machine. “Sedentism often promotes affluence… and humans such as these, blessed with a rich abundance of resources, paved the way for even more unique ways of living. We’re about to head west to meet a group of people who were among the first to kick-start one of the most revolutionary inventions of all time! And the strangest part of that story is that the process of invention was totally blind: no one knew what they had created until it was too late.” 

…

_The Levant, 11,500 Years Ago_

You find yourself doing a double-take. Peridot has taken you to what looks like another open woodland, almost similar to the one from Japan. But the dawn air is a bit warmer and drier, and the ground feels a tad dustier. There are grasses and wildflowers here too, but of different varieties. 

As Peridot makes some repairs on the time machine, she fills you in.

“The road to agriculture - growing and raising your own food in an altered environment - was not a simple one. Your Earth scientists have spent generations trying to figure out the whys and hows of farming. They have developed many ideas as to what caused people to select specific kinds of plants and animals and change them through cultivation and domestication, but the process itself may have been different for everyone. Meaning that these ideas may hold true for some, but not for all… so the truth may never come to light. That’s because agriculture, like pottery or bows-and-arrows, was created independently across the world at widely different times, in at least 8 or 11 areas or more! For now, let’s just spend time observing some of these different peoples, to see how the world’s most valuable crops and farm animals emerged.”

With a couple of tweaks, Peridot finishes her repairs, giving the time machine a good smack. Once again, you climb aboard, and Peridot takes the pod for a nice hover along the ground. Southwest Asian trees and shrubs pass by the window. You spot some gazelles leaping across a forest clearing. 

“The very first humans to make the transition to agriculture lived here in the Levant, the westernmost part of Southwest Asia,” Peridot says. “The Levant itself makes up the middle of a band of territory that historians have named “The Fertile Crescent”, which is exactly what it sounds like: a rich land full of diverse plants and animals that sustained human populations in an otherwise parched and dry part of the world. It stretched from the Nile River all the way to the Persian Gulf, flourishing in conditions created by the end of the last ice age. It was in the Fertile Crescent, like on the Japanese islands and elsewhere, that foragers began to settle down and become sedentary. The ones we’re about to visit, called Natufians, were among those who first invented agriculture.”

It isn’t long before the Natufian settlement is found. Peridot parks the time machine safely in some bushes, and opens the hatch to look around.

“The coast seems clear. We’re gonna go stop by, say some hellos, and maybe get some up-close insights into the lives of these ancestral-farmers. We’ve been lucky so far… heeheehee.” Taking her lead, you follow Peridot towards the settlement, which is immediately much more impressive than anything seen up to this point. You make out something like 50 houses, with strong but low walls made of solid rock all bound together without mortar, with thatched roofs made of grass, brush, and animal hides. This is no ordinary settlement, but a proper village.

There is small activity about as people are now awaking. One couple exits their home. You can’t help but notice how they almost rise out of the ground through their homes. And then it hits: the houses are semi-subterranean, with the lowest levels dug out of the earth and accessible by a small staircase. That’s new.

“Play it cool.” Peridot whispers, as a trio of tall and well-built women approach you two. They are tan-skinned, with long, dark hair that is covered by extensive headdresses made of bone beads. Their bodies are covered with tanned gazelle-hides, further adorned by bone and shell jewelry. 

“Oh! We weren’t expecting visitors. Are you here to trade?” one says, clasping their hands together. Another joins in, with a spring in their heel, “I’m afraid all we can spare are acorns and almonds for now… we’re still needing to make some new stone points to replace the old ones.”

“Thank you ladies, but we’re not here to trade! We’re… eh… explorers, hoping to… learn the ways of our neighbors.” Peridot quips, as you scratch your arm awkwardly.

“Ahh, sounds like you want to trade information then,” the third Natufian girl replies, smirking. “Well, cutie… that I think we can do. What’s on your mind?” 

Peridot blushes, pulling at her collar, “eheheh… you’re very kind. Um… see… we’re interested in branching out our people’s diet, and we were wondering if you knew of any kinds of food that we might like?”

The three girls look to each other and talk it over, before nodding and turning back to you. “Okay then, you’re in luck. We were just about to visit our gardens to make the year’s harvest. There are plants there that I think you may be interested in,” says the first girl.

“Great!” Peridot cheers, before the third woman walks up to her and bends down to get at eye level. She towers over Peridot intimidatingly, with a grin. “But… this is a secret location. You’re gonna keep your mouth shut, and you’re gonna work to get your meal. How’s that for a ‘trade’ sweetie?”

“Ehm… uh… yes! We will… we will certainly keep your garden a secret!” Peridot shivers, before giving a formal salute, “You have my word, as a Crystal Gem.”

Two of the Natufian women look to each other.

“Crystal Gem?”

“They’re definitely not from around here.”

…

The walk to the Natufian garden is not a short one. The women lead you two through several inconveniently bushy parts of the forest, past jagged rocks, and over a small river just to reach the location. At first, there doesn’t appear to be a garden at all, just a mass of different wild plants, but soon the women clarify things.

“We find these plants growing all across the forests of our lands,” explains Narkis (the first woman who greeted you). “Many of them are quite delicious if you know what you’re doing.”

The second woman, Basima, fumbles through her basket as she elaborates, “We’ve been raising plants here for many years, protected by the groves of oaks. Every village has their secret garden, since we often trade with others for food and supplies, so it’s sort of an unspoken rule that the areas be kept secret to all but your own people.”

“It’s a sacred place,” adds Avira (the stern and flirty one). “This garden has provided us with good, hearty food that lasts a long time under storage. We owe it our care.”

“Wow, that’s amazing.” Peridot comments, astonished by the woman’s devotion. She turns to you, pointing down at the grasses discreetly. “These plants right here? Some of the very first species that will be domesticated. You’re looking at wild peas, wild rye, and perhaps most important of all, wild wheat.”

“Oh shoot!” exclaims Basima, furiously. “I was afraid of this.”

“What is it?” asks Avira, running over with Narkis.

“Are we too late? A lot of the wheat here has ripened already.” Basima replies, bending down to poke a stalk. With even this light brush, all the seeds collapse from the ears and spill onto the ground. “We won’t be able to use it.” 

“No, we’re right on schedule.” says Narkis, turning to you and Peridot. “This happens sometimes. Wheat is a pretty fragile plant if you’re not careful.” She turns back to her companion. “Let’s just take what we can and go.”

“Here… you’ll need these.” Avira hands you and Peridot two grass-woven baskets and a pair of shearing tools. The Natufian girl points to the devices, “you ever seen one of these before?”

You inspect the tools: the handle is made of a leg bone that has been carved with intricate patterns; the far end curves slightly and is marked by a series of very sharp stone flakes that have been embedded and glued to it.

“No, I don’t think so.” Peridot lies, looking up to the girl.

Avira smiles, “that right there is a sickle. We use it to harvest the plants here, but you have to cut them just right. What we want is the ears of grain and the uppermost stalks. Don’t worry about the stems, they’ll wither away on their own. Now get going.”

For the next hour, you and Peridot are helping the Natufian girls collect their wild crops. Narkis demonstrates the basic motion: you are simply cutting the wheat over the basket to catch it. The relatively dry weather makes this repetitive work a bit much on you, but Peridot occasionally manages to sneak you a drink of water from a bottle she had been saving.

Peridot herself notices some red flowers growing amongst the wheat and rye and turns to Basima. “Hey!” she calls, “do you want me to collect these too?”

“Oh no no no!” Basima replies, giggling. “That’s not food. I planted those there myself. I think they’re pretty.”

…

Eventually, you and Peridot return to the village, sweating and hauling baskets of wheat, rye, and peas on your backs. The women are having no such trouble, and Avira shows off a bit. The five of you descent into one of the bigger houses of the village. The inside is cool and nice, and you get a good view of how the roof works: the brush is supported on large wooden trunks. All around you is an assortment of different objects - bowls and baskets, pestles and mortars - that you immediately guess is for working food. Narkis is preparing a fire at a rock-hearth, located at the center of the house.

“Okay, place those baskets there and we’ll get to work processing everything.” Avira commands, pointing to one of the stone walls. “Chop, chop! Let’s go.”

The first job is pretty simple. You and Peridot find yourself removing the ears of wheat into big wooden bowls. Narkis carefully places some heated pebbles into the bowls, which starts to smoke and dry out the ears. Then, Avira has you transfer the ears into a larger mortar made of oak wood. Guiding you, she demonstrates the process of crushing the ears with a blunt, wooden pestle. She makes sure every last seed has been removed this way. Finally, you delicately separate the seeds from everything else back onto a new mortar.

“Now comes the fun part.” Avira says, chuckling. “Just beat those seeds with the pestle as much as you can until they get all powdery. After that, you can relax, and we’ll take care of the rest.”

After several repeated attempts to get the seeds fully crushed, you begin to notice that you’ve essentially made flour. Curious.

“Great! Now, gimme gimme.” Basima smiles, waggling her fingers as you and Peridot hand her the multiple bowls of flour. 

“Narkis, if you please.” Basima asks, to which her friend gives her some bowls of water. Before long, Basima has mixed everything and made a sandy-colored dough, which she molds into little rolls. The places them along a wooden tray and sets them to bake on the hearth. 

There’s a knock by the entrance, causing everyone to turn. A man, dressed with bone beads atop his groomed hair, enters the house carrying several pieces of grilled meat on a sharp stick. “Anyone up for some gazelle? I just cooked it!”

“Oh Jorai, you doll!” Narkis runs up to the man and gives him a warm hug. “Yes, we would love some. You’re just in time… we’re preparing some bread right now. Care to join us?”

“I’d love to, but unfortunately I need to go inspect the storehouses. We keep getting mice.” Jorai replies, shrugging. “I’m at my wits end.”

“I’m sure you’ll think of something.” Narkis encourages, patting the man’s shoulder. 

Peridot turns to you quietly, “how are you holding up?”

You sigh, rubbing your arms.

“Don’t worry, we’ll be out of here soon. Let’s get a quick bite to eat first and then we’ll split. I’ve always wanted to try Natufian bread… it’s one of the oldest baked goods ever crafted.” Peridot grins, looking at the rolls cooking on the hearth. “The funny thing is… it seems that the Natufians perfected alcohol long before they figured out how to make bread. Earth scientists have found the remains of really old breweries that predate the production of the first bread. You probably wouldn’t like it… it’s supposed to taste like a bitter beer with the consistency of grits. Hops wouldn’t be used for many thousands of years so… there’s not any flavor to it.” 

“Okay! Who’s hungry?” Basima exclaims, using a pair of utensils to remove the bread rolls from the fire and onto a set of bowls along with the helpings of gazelle. She passes them around as everyone sits comfortably by the fire. 

Sniffing the buns, you blow on them to cool them off, and carefully pick them up to take a bite. It’s almost like dull multi-grain bread.

“Now you get to enjoy the fruits of your labor.” Avira says proudly, crossing her arms. “As you can see, this is all very simple to do. If you can locate a nice forest where wheat grows, you can start your own garden and make your own bread! How does that sound?”

“I think our people will very much enjoy this.” Peridot responds, a little to into the food. “Thank you for all your help.”

“You’re very welcome… babe.” Avira scoots over to Peridot, nudging her with her shoulder, to which Peridot groans.

…

After staying another half-hour, swapping stories, you and Peridot leave the village to a string of goodbyes. To get your hypothetical garden started, Avira has gifted Peridot a freshly-made sickle and a bag of wheat seeds. 

She admires it as you both walk to the time machine. “Well… that was nice. I think we got a very intimate look at Natufian life. You see, for many generations Natufians will visit their gardens and collect wild grains like wheat and rye for use as food. They wouldn’t have viewed them as crops or inventory, but as things of beauty in a garden that just happen to have a good use. Did you notice their frustrations with the fragility of the wheat? How easily the seeds spilled from the ears?”

You nod.

“Well,” Peridot continues, “in their harvests, they always favored the ears of wheat that remained intact. They selected the best grains that suited them! Over time, like a few hundred years, the Natufians will pick these tougher plants more and more, even going so far as to plant them in little gardens near their homes for easier access. The fragile grasses will gradually disappear from the gene pool, while the sturdier grasses - those that can only be harvested with a sickle - will proliferate. And a plant like that can no longer survive in the wild, because it would never germinate without human intervention. Presto! You’ve just domesticated wheat!”

Climbing into the time machine, Peridot turns the dial and begins fastforwarding through time. The village before you, with all its human occupants, gradually shifts, with the old homes replaced by newer settlements and newer occupants. 

“That process has been estimated to have occurred over a period of 200 years or so, and by the end of that span of time, Natufian society changed completely! They were no longer hunters-and-gatherers that tended to wild plants… they had become true farmers. And this change only became more pronounced after that.”

Peridot ends her time-jump, and the date reads: _10,300 Years Ago._

Getting out of the time machine, you find yourself rubbing your eyes in shock. 

Everything has really different. The circular, semi-subterranean homes have been replaced by much larger, rectangular houses (and there are many more of them). The stone-brick construction is now gone, and the walls of the buildings are carved out of mud-bricks instead, though the roofs are still made of thatched foliage. Instead of being spaced apart, the houses are all next to each other, connected by small alley-ways, each with their own yards and multiple rooms. It’s not unlike a city block.

“Agriculture changed everything.” Peridot begins, gesturing to the massive village before you. “The cultivation of grains like wheat, rye, and barley took off among many settlements around the Fertile Crescent. Now that more and more people were growing crops and distributing them to their families and friends, more and more people could be supported. That’s because farmland can create many more resources than those found in the wild: they’re more productive and the rewards are more readily available than a week’s worth of hunting. Provided that there isn’t a rough winter or a terrible, stormy summer, domesticated crops were guaranteed sources of food that could be stored and saved for other days. As fields grew, so did the villages that tended them, and with more hands to work the land, so the fields grew even more. A positive-feedback loop began, and the practice of agriculture spread far across the Fertile Crescent, taken up by many different peoples living there.”

Peridot handles her bag of wheat with care. “The peoples of the Fertile Crescent gave the world the first domesticated wheat, rye, barley, lentils, and peas. These were the wild plants that they gathered and turned into human-dependent crops. On the animal side… the transition from hunting to raising livestock was a different.”

You notice a farmer herding in a collection of sheep into a small pen. They’re rather gangly animals, with curved ram’s horns and small manes on the undersides of their necks. The sheep yell as the farmer gently nudges them inside with a small whip-shaped stick.

“The Natufians had started out as hunters of gazelles, rabbits, and other species living in the forests and highlands of their world. Even when they started relying on domesticated crops, they were still hunters of wild animals. Eventually, however, stocks of wild game like gazelles began to vanish as the Natufians seemed to be overhunting them. Their attention turned to a few species that tended to be highly social, easily approachable, and quick to breed: sheep, goats, cattle, and pigs. Overtime, the peoples of the Fertile Crescent began to regularly manage these wild herds, killing off the tougher, meaner individuals and leaving the rest to continue reproducing. This is the same process that these humans used to domesticate plants: artificial selection, because the organic populations were being altered by human hands. Eventually, they started moving these managed herds into areas where they could be watched and tended to daily, like that fenced-in pen over there.” 

Ushering you back into the time machine, Peridot punches in new coordinates.

“That is the birth of agriculture in a nutshell: humans started favoring specific species of wild plants and animals and dedicated time to perfecting them. A change that dramatically transformed their lives from the work of hunting and gathering to the long labor of tending land and raising crops and livestock. It’s not something that anyone would have sought out for its own sake… no one got up one day and was like “I’m going to invent farming!” It was just a slow, unconscious, societal change. And as I’ve explained before, it’s a process that happened independently in many parts of the world and at different times. I’m going to take you to two more places to get an idea of how the people living there started agriculture of their own.”

…

_Present Day China, 9,000 Years Ago_

Peridot takes the time machine for a small cruise along a wide river, interspersed with intense, raging waterfalls. The area surrounding the river is dry, rocky, and mountainous, bordered by dense forests of conifer trees. 

“It seems that agriculture developed twice in East Asia, along the two major rivers that flow through the country of China in modern times: the Yellow or Huang He River in the north, and the Yangtze River in the south! We’re sailing down the Yellow River right now, if you couldn’t tell by the yellowish tint in the water… that’s all silt being carried down from a great plateau called the Loess.” Peridot gestures to the water, where you can’t help but grimace at the dirty water.

Peridot notices this: “I know it doesn’t look very nourishing, but for the type of grass that grows wild in these regions - millet - the water is more than enough. After all, millet likes dry soils, and the soils of the Loess are smooth enough to support plants like that. Given its plentifulness, it’s no surprise that the foraging peoples of the Yellow River basin took a liking to it.”

Moving down the river at an increased speed, Peridot happens upon a small village located just beyond the riverbank. Their homes are semi-subterranean houses with straw-roofs, not unlike those of the Natufians, but your attention is drawn to the massive series of pits dug into the earth near the homes. They’re covered by wooden posts, and you notice a woman dumping millet grains from a clay pot inside one of the pits. 

“It’s likely that East Asian foragers tended to wild grasses in just the same way as the people in the Fertile Crescent, selecting the kinds that they liked and processing them into food. However, while the Natufians made use of wooden sickles, Yellow River peoples fashioned spades out of stone to cultivate their millet. Because, again, millet grows in the soft, damp soils of the Loess, unlike the dry, forest dirt of Southwest Asia which supports wheat and rye… spades are just easier to use here than sickles.” 

Peridot takes the pod and travels around the village, passing by small pens of pigs. There are rows of women in the fields, digging up millet plants and transferring them into clay pots. Taking one last look, Peridot sets the time machine into overdrive and before long you’re cruising at a decent pace away from the Yellow River.

“For the people living along the Yangtze River, their lands were notably different.” Peridot explains, checking the compass on the time machine’s panel. You’re traveling southward. “It’s much wetter and warmer, the perfect place for one of the most important crops of the present day, rice! Rather than damp soils, rice prefers to grow in shallow water, and this reliance on liquid means that you don’t have to wait a year to harvest it! Rice always replenishes itself after a few months. That was a big draw for the people of the river valley.”

Finally reaching her intended destination, Peridot slows the time machine down to a reasonable pace. The Yangtze River before you looks very calm, almost miniscule compared to the spectacularly steep mountains parallel to it. Cruising down the river, Peridot searches far and wide for signs of human activity. The mountainous terrain slowly gives way to marshland and forests of pine, where ferns just litter the ground. A trio of rhinoceros are drinking from the river, and one looks up to observe the strange pod hovering past them. You spot something in the distance, grabbing Peridot’s shoulder and pointing towards it. “I’m on it.” Peridot pilots the time machine, approaching a small fleet of boats. There are men on the boats, dressed in leather hides and sporting groomed facial hair, fishing for catfish and carp. They’ve already caught a fair amount of food.

“Wow! We must be close to a village.” Peridot grins, piloting away from the fishermen and further down the river. Sure enough, you approach the most remarkable settlement yet, seemingly built into the river itself. With the area basically founded on marshland, all the wooden houses are supported on either on stilts made of pine logs or heaps of raised earth. The entire village is surrounded by a tall, wooden fence, with an opening at one end: this is likely where the boating fishermen leave and enter their home. There is a little bit of movement outside, where children are running after each other on the wooden planks and bridges connecting the homes, and men and women are constructing clay pots. 

Taking care not to disturb the peace, Peridot finds a group of women working in the shallows neighboring the village. They’re hard at work sowing rice seeds into the water beneath their feet.

“Foragers here began to select for hardier rice crops, choosing the plants that retained their seed and needed human aid for release, and they too began to slowly rely more and more on these simple grains than many of the wild plants that were growing around them. Thus began a repeated cycle of work for the people of the Yangtze: taking every few months to collect their rice crops, and sowing the seeds for the next cycle. They took care to manage the waters, guard their plants from weeds, and filling their baskets and pots to the brim with seeds. The simple exercise of gathering wild rice turned into a laborious series of chores. But it was fruitful work, because like the Natufians this bounty of rice crops ended up feeding and supporting greater numbers of people. So, generally, life was pretty good here.”

Peridot punches in new coordinates. “In time, the millet-farmers of the Yellow River and the rice-farmers of the Yangtze River perfected their craft, expanding their populations, and eventually coming into contact with each other. In all that time, societies changed, and the seeds of Chinese civilization were sprouting. But… eh… I’m getting ahead of myself. Onward!”

…

_Present-Day south-central Mexico, 7,000 Years Ago_

“Agriculture in the Americas is a bit of a different story.” Peridot begins, taking the time machine over great subtropical forests. “While there were many areas across the two continents where the conditions were notably favorable and resources plentiful enough to settle down and create great villages, most everyone didn’t for the longest time. Native American populations remained surprisingly low across their lands, probably because they were relative newcomers here, compared to places like Africa or Eurasia where there has been a continuous human presence for tens of thousands of years. And yet, the sparks of agricultural development had been underway from an early age.”

Passing over some clearings in the rainforest, you observe groups of people using fire to clear away some of the trees and brush. Gray smoke rises above the canopy.

“Native Americans living in forested environments often managed their hunting and gathering grounds by burning away parts of the land. This form of weeding encourages new growth of plants and increases the productivity of the soil, further providing food to families and communities. Out of all the wild plants utilized by these peoples, the first American crops to eventually be domesticated were bottle gourds and squash.” Peridot says, drawing your attention to one of the women below, drinking water through a gourd just like a canteen.

“Bottle gourds - or calabash - likely floated to the Americas from Africa, since those found here are closely related to the African species. They’re quite durable and resilient plants: you can hollow out the toxic insides and make all kinds of things, like water bottles or containers for food. Squash was used in a similar way, although the seeds inside are actually edible when you roast them. Both these species were being cultivated by 10,000 years ago, during a time when all Native Americans were still foragers of wild foods.”

Moving onward, Peridot eventually leaves the rainforest, coming upon the increasingly dry shrubland and hilly terrain.

“By 7,000 years ago - the time which I’ve taken you - new crops began to be utilized, including another species of grass that feeds billions of people across the globe in the present day, maize. You may know it as corn, and I myself know a thing of two about that, given all the time spent growing it on Lapis’ and I’s farm. Ahh, those were the days.” Peridot sighs, leaning back. “The funny thing is… the ancestors of corn looked remarkable different from your big, yellow, on-the-cob varieties. In fact, when it first started to be cultivated 7,000 years ago, it wasn’t bred for use as a grain! Just watch.”

Peridot moves the time machine towards a small depression in the landscape, where a group of Native Americans has settled down for the evening by a small cave site. A great fire is roaring nearby as several of the adults are laughing and telling stories.

Settling the pod down just close enough, Peridot points to one of the women, picking out tiny, diminished cobs from a gourd and chewing on them.

“Whereas wheat, rye, rice, and millet became staple crops for the peoples of the Fertile Crescent and East Asia, corn did not form a major part of the diets of the Native Americans who grew them, which lived throughout the southern reaches of what will become Mexico. The wild ancestor of corn, a curious plant called teosinte, does not produce big enough cobs to make things like bread. Instead, Native Americans here simply chewed on the cobs and enjoyed the sweet, sugary taste of the juices. Corn was domesticated first as a kind of candy!”

Chuckling, Peridot pulls out her bag of wheat and fidgets with it. “Eventually, these native peoples of Mexico will figure out how to ferment the seeds and create a kind of beer that will later be known as chichi. That will pick up remarkably quickly, and corn will spread outward across Mexico and beyond, to many different parts of the Americas. And, in time, some groups will settle down, become sedentary, and kickstart their own societal changes, just like the Natufians, and the people of the Yellow and Yangtze Rivers, and in many other regions around the world. Don’t worry, we’ll check up on them in time.”

Turning to you, Peridot pulls out her tablet.

“One of the most important things to remember about all of this - sedentism, agriculture, domestication of animals - is that the process wasn’t universal. Many peoples will continue to live as hunters and gatherers, relying on their foraging to provide them with food. They’ll build temporary structures, trade with their neighbors, and share ideas, in much the same way as our friends of Ice Age Europe 30,000 years ago. And other people will pick up the sedentary lifestyle, but never develop agriculture, like that family of Jōmon from earlier. What I’m trying to say is, agriculture was never an ultimate goal of human societies. It was an accident! People never meant to invent it, it just happened over time due to the complex series of environmental and social changes brought about by the end of the glacial periods. And for all its benefits, agriculture brought on some major issues as well.”

Flipping through her tablet, Peridot pulls up a photo of some toe bones, excavated from an archaeological site. They don’t look healthy. “Farming takes up a tremendous amount of labor for the people who practice it. Once those humans began to spend more and more hours working their lands, planting and harvesting and processing their crops, their bodies started changing. The first instances of arthritis show up in the archaeological record during the origins of agriculture: this lady spent so much time on her feet, kneeling down and working, that her toes became deformed and worn down.”

Turning to another picture, this time of an early farmer’s teeth, plagued by decay. “By limiting their diet to a few select crops out of the abundance of wild species surrounding them, farming peoples often didn’t get the whole suite of nutrients that they needed to carry on their daily lives. Their health, in general, declined. Dental hygiene was pretty much ruined as generations of feasting on grains, grains, grains promoted the spread of bacteria that produce cavities. And that’s not to forget the health of the body as a whole: growth rates and life expectancies fell for many of the farming populations. And don’t even get me started on the swapping of parasites and diseases between livestock and humans as the two started living in close contact… yuk!”

“Perhaps most difficult of all,” Peridot finishes, putting away her tablet, “is that one bad season can place enormous pressure on farmer populations. By depending on such a small helping of plants, you risk having nothing to eat should a plague or winter frost wipe out all your fields. More often than not farmers couldn’t turn to wild resources as a backup, because they had dramatically changed their surrounding landscape through forest clearance, overgrazing by livestock, or other means. They made themselves vulnerable.”

You place a hand to your mouth, and can’t help but look at Peridot with a shocked expression. “Yeah, I know… it’s tough to think about. Agriculture was a game changer in more ways than one. A blessing and a curse. It kickstarted many of the great societal and cultural changes that led to the major civilizations of the world, and it introduced a spectacular world of culinary arts, creating organics that gave more food to more people than ever before. But it also took away the benefits that came from a foraging lifestyle, where hunters-and-gatherers tended to be healthier, longer-living, fed on a well-rounded diet, and worked less hours. I’m a gem, so those matters don’t affect me personally. That’s all on you… which life sounds better?”

…

**_To be continued!_ **

**Notes for the Chapter:**

> Special thanks to Chris Scarre et al. "The Human Past: Fourth Edition" (2018), Paul Bahn et al. "Archaeology: The Essential Guide to the Human Past" (2017), Steven Mithen's "After the Ice" (2003), Brian Fagan's "The Long Summer" (2004), MacPhee's "End of the Megafauna" (2018), and Peter Watson's "The Great Divide" (2011) for information.


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